AppearanceBrook is an extremely tall skeleton dressed in formal attire complete with top hat and cane. Despite having no skin, his head still has an afro which he says is because his hair has deep roots. Brook's coat, top hat, pants, and afro are black while the inner linings of his coat are yellow orange. The ribbon tied in between his coat and around his neck is blue. The outer covering of Brook's cane sword which he carries is purple. Also, due to his many years of seclusion his clothes have become somewhat tattered.
Before his death, Brook was a tall skinny 38 year old man with a rather distinctive face. He had a slight goatee on his chin and some side burns. He typically wore shades. On his forehead was a scar that slightly resembles a diagonal omega sign (Ω). This scar was retained in his skeleton state as a distinctive crack across his skull. Brook's facial appearance, accompanied with his style of clothing, resembles a type of appearance that is commonly associated with various music artists such as Ozzy Osbourne, Slash, and other musical celebrities with similar features.
In Gear Spirit, Brook is presented with a different color scheme than the one depicted in both the manga and anime. The color of the collar of his coat is gray while the ribbon and the frills coming out of his coat are purple. In some artwork within the game, Brook's nose socket is uncolored. The outer covering of Brook's cane sword is also colored red in the game. This color scheme is so because the game was developed before an official color scheme from the manga was presented.
According to Oda, Brook most resembles a horse. He is identified by the colors black and white, and he smells of tea.
PersonalityBrook is an eccentric character with, like the other Straw Hat Pirates, a distinct personality of his own. While he looks like, and claims to be, a gentleman, he possesses very bad manners such as asking to see ladies' panties (in a mermaids case he asks if they can lend him some money) and waiting impatiently for food (a trait shared by Luffy).
His reactions to different occurrences can be somewhat extreme, often comically so. For example, when the Straw Hats were alarmed at him for being a living skeleton, he forgets the object of fear is actually himself and also begins to panic. Although he tends to display more extreme emotions of things, however, Brook also has been known to over relax himself when he is told to stay calm. He is also very patient, having stayed on his former crew's ship for years, waiting for the day in which he would be eventually reunite with his shadow. However, due to his rudeness he can also be impatient about things like waiting for dinner to be served. Brook's most notable trait amongst others, however, is that he cracks "skull jokes" about himself being a skeleton complimented with his distinct laughter of "Yohohoho" even if there is no one around to hear him.
Brook is a great lover of music. Whether it be through happy or sad times, music is what generally keeps Brook going. As a result, his love for music often reflects itself in various other aspects of his character such as in his fighting style wherein the names of his attacks are derived from various musical songs and dances. He overall gives himself a musical theme so noticeable that while he was alive in his first life, he was called "Humming Brook" by the authorities.
In contrast to the other cowardly crew members own fears -Usopp(fear), Nami(survival) and Chopper(cautiousness)-, Brook's fear is more down to Earth, abide he fears the things that are not normal. An example would be that Brook is easily scared by the ghosts and zombies (despite technically being undead himself). In order to fight the various Thriller Bark Creatures without fear when he encountered them, Brook convinced himself that if he sings while fighting, he wouldn't be afraid of them (though he starts running in fear when he stops singing). This singing while fighting, however, had a side effect of making him seem like a more sinister creature to the zombies- a rather ironic fact due to him being the contrary and the fact the song he sings during battle being one of life and joy than one of ominous threat and evil as perceived by them. Because of this, despite his equal fear he was given the name of "Humming Swordsman" by the zombies and was ironically feared by them in turn. He apparently doesn't like moving fast, evident when he was in the more intense rides at Sabaody Park. Linked to this is moving at high speeds via the Flying Fish Riders flying fish or theme park rides and fighting a Pacifista cyborg there was little chance to win against. Comically, most of these fears are things he himself has the potential to unintentionally cause such as being an almost living skeleton that can run fast, that most people would have little chance to win against.
Before encountering the Straw Hats, Brook was very lonely while floating adrift on his ship and longed for the company of other people. He initially accepted Luffy's offer to join the crew and invited himself over for dinner upon arriving on board the Thousand Sunny just so he could interact with the crew and fill the void that he experienced all those years. Also, while possibly one of the oldest pirates "alive", Brook still retains an air of childishness about him that enables him to behave in a manner similar to Luffy and Chopper, noted by the ease with which he participates in their child-like antics.
His distinct personality and laughter allowed Nami, Usopp and Chopper question a "guardian" of Hogback's lab, Ryuuma, who had Brook's signature laughter and personality. This was because Ryuuma possessed Brook's shadow until he was defeated by Zoro, upon which Brook's shadow was returned to its rightful place.
Awkwardly, Brook has a tendency to lack common sense in slightly frantic times. For example, when Luffy falls into the water, Brook (and Chopper for that matter) jumps into the water, despite being a Devil Fruit user himself. He also has tendency to accidently go on rides that go obviously fast, and sit out on slower rides.
CrewThe Straw Hats were immediately wary of Brook prior to his initial entry into the crew, but this changes after the events from Thriller Bark: Franky is moved to tears upon hearing Brook's backstory, and the rest of the Straw Hats gain respect for him after hearing about his devotion to keeping his promise to Laboon. Before he officially joined the crew, only Luffy made friends with him, due to finding him hilarious; the two even goofed about in the same manner during their dinner on the Sunny. His eccentric personality often gets on the crew's nerves, showing no appropriate respect for Nami and even Robin when he asks to see their panties, and cracks Skull Jokes in serious situations which often leads to him being beaten up, even shattering Robin's normally limitless patience. Nevertheless, Brook's sense of irony and music can enlighten an entire organization as big as the Thriller Bark Victim's Association.
FriendsBrook cares a lot for his afro. Being the only part of him that didn't rot away after he died, it means a lot to him. It is the only thing he believes that Laboon would still recognize after fifty years. Since it won't ever grow back again should it be cut, Brook is ever more protective of it.
Laboon from Brook's memory
“ In addition to losing our nakama, my face, my body, I've lost it all. Even if we met again you wouldn't recognize me at all in this skeleton form. I don't have anything left but they all said... this head of mine made you laugh...!!! I'll protect this look to the end because I'm coming to see you. I just hope you're waiting at our promised cape...!!!
- Brook about the need to protect his afro.
Because of the promise Brook and the rest of his crew made to Laboon, Brook feels obligated to meet up with Laboon in order to fulfill that promise. He feels that Laboon wouldn't forgive them for dying irresponsibly in the Grand Line.
EnemiesWhile alive, Brook encountered many enemies during his journey through West Blue and the Grand Line, including the group that killed him and his crewmates. He also earned a bounty from the Marines in this time.
Because of the mess he made back five years ago in Thriller Bark, three of the Mysterious Four know how troublesome he was. Dr. Hogback, in particular, greatly fears him, mainly because Brook once had him at sword point 5 years ago and knew the weakness of the zombies. Only Perona doesn't know of his doings because she was asleep at the time and ignored Kumacy's attempts to wake her. Brook's main enemy of the time on Thriller Bark was Ryuuma who was the zombie who was animated with his shadow.
Abilities and PowersBrook is a musician who is able to play any musical instrument. He usually uses a violin to play his music. His musical abilities are so good that Laboon used to sing along to his music when they were together. When Brook fights, his battles often have a comical element to them. Examples include putting several members of his crew asleep while fighting the Flying Fish Riders, playing dead halfway through a battle or launching at an enemy with erroneous results. 
Brook also knows how to purify the various Thriller Bark Creatures with sea-salt.
While he was still alive, Brook ate the Yomi Yomi no Mi. The fruit allows the user to come back to life for a second time. Though his soul wasn't able to find his body in time before it decomposed completely to a skeleton, he gained some advantages that would otherwise be impossible to do without being a skeleton supported by Devil Fruit powers. One advantage is that because he's just comprised of light weighted bones, he can use his speed and light weight to run across water, however like all Devil Fruit users, he still can drown when submerged. With the aid of the Devil Fruit powers, he is also able to function like a regular human being, and retains all the strength he had when he still had actual muscle mass. He is able to do normal acts such as drink, eat, cry, digest, and even "poop" normally. He has also proven that calcium (such as in milk) will rapidly heal any damaged bones. Due to his light-weight skeleton body, he can leap great distances and run fast and can also store things in his skull cavity such as a Tone Dial.
Fighting StyleIn his cane Brook hides a sword known as a shikomizue, which he can use to great extent. His fighting style while using it resembles classical fencing and iaido. Brook's main advantage is the speed of his attacks, combined with the light weight of his skeleton body, he's able to deal extremely accurate blows and quick maneuvers before his opponent can react (once taking down and purifying a whole swarm of Surprise Zombies in a fraction of a second) that are much swifter than he was when he still had flesh and blood back in his mortal days. With these advantages, Brook excels best at fighting and taking down large enemy numbers of average fighters on his own. Despite not retaining any muscle tissue, it seems that Brook can still grow stronger over time, as he said to Ryuuma that he is stronger then five years before then.
Brook's signature attack as of yet is known as 鼻唄三丁:矢筈斬り, "Hanauta Sanchou: Yahazu Giri", loosely translated into "Three-Verse Humming: Arrow-Notch Slice". The attack is the fastest cutting technique of his kingdom's assault squad. It was originally named "Requiem Banderole", but was given the other name by his old nakama. Due to the attack's blinding speed and Brook's distracting humming, enemies often don't notice they have been hit until after Brook has sheathed his sword.
When the need arises, Brook can also employ his music to aid him in battle. His technique, "Nemuriuta Flanc", loosely translated as "lullaby Parry", shows this, where he strums his violin with his shikomizue like a violinists bow, creating a soothing tune that renders anyone who hears it immediately asleep.
Although an extremely fast swordsman, his skills are not of the same caliber as Zoro's, the Straw Hats other Swordsman. While Brook had been unable to defeat Ryuuma no matter how hard he fought and while Ryuuma only used a fraction of his power, he noticed that Zoro was able to defeat him at full power with only two of his swords. At the Sabaody Archipelago he struck a Pacifista with a high speed sword attack, yet failed to do much damage to it and had to be rescued from this result afterwards. However, when Zoro attacked the same Pacifista, the results were much different. Although not on par with Zoro, he was able to keep up, visually, with what Zoro was doing while he fought Ryuuma showing that he is still a very skilled swordsman.