If The Book of Boba Fett set out to do anything, it was to develop Boba Fett as character beyond what many people thought of him based on his brief appearance in the original trilogy. Not only has much of the character's history from the old Legends continuity been scrubbed in favor of a new story, but the trajectory of Boba's character growth has been changed in some pretty significant ways after the events of Star Wars: Return of the Jedi and The Mandalorian Season 2 (when he made his exciting reemergence).
Some of these changes were met with widespread fan acclaim, while other changes faced a little more scrutiny. Either way, it's clear that The Book of Boba Fett wanted to show a deeper, more emotive Boba than fans were expecting. Whether the show succeeded is up to the fans.
5 Boba is a Nice Guy (Sort Of)
Many fans might remember Boba Fett's cold and seemingly merciless personality from The Empire Strikes Back. Back then the character was known for two things: disintegrations, and having the guts to back-talk Darth Vader. Starting with The Mandalorian season 2, however, Boba began to exude a bit more humanity, though he still retained a fair bit of devilishness in his personality.
Now, with The Book of Boba Fett, Boba is a noticeably warmer person than before. Not only does he make a point treat other people with respect (including some of his enemies), he goes out of his way to protect the town of Mos Espa from the Pikes and stop their Spice trade. He even goes so far as to put his life on the line for whom he considers "his people." Cad Bane even mentions how much softer Boba has become in his old age, to which Boba himself agrees.
4 Survival Of The Sarlacc Pit
Boba falling into the Sarlacc Pit has been one of the most universally disliked moments in Star Wars history. It quickly became retconned in expanded media, though the story has changed a number of times. The Book of Boba Fett finally gives a definitive answer not only as what Boba was doing while trapped in the pit, but how he escaped and what happened to him afterwards.
Originally, Boba survived the Pit with the help of fellow bounty hunter Dengar, who found him half dead after having detonated his jetpack while inside. In the show, Boba, while still trapped within the Sarlacc, just barely escaped by using his flamethrower to burn a hole through its flesh and dig his way out through the sand, but not before stealing a bit of air from a long dead stormtrooper's helmet. From there, Boba's armor was then stripped from him by the Jawas while he lay unconscious, leaving him open to be captured by Tusken Raiders.
3 Boba And The Tusken Raiders
Some of the best parts of a show are undoubtedly those which feature the Tusken Raider tribe that took Boba in after he escaped the Sarlacc Pit. This relationship was hinted at briefly in The Mandalorian via Boba's robed attire and use of a unique Gaffi Stick and rifle, but there was never an official explanation until The Book of Boba Fett showed him being taken in by Tuskens and staying with them for years as one of them.
The Tribe, in essence, became Boba's new family, one to take the place of the father he lost on Geonosis in Star Wars: Attack of the Clones. Unfortunately, Boba would lose this new family just as he lost his father when he was boy. This ultimately forms the basis of his motivation in the show: he wants to start a new tribe, a new family, with which to rule Mos Espa. This also explains the function of Cad Bane as a foil for Boba Fett's character. He is a loner who only looks out for himself, and considers attachments to be a weakness.
2 A Bounty Hunter No More
Boba's desire to be a crime lord was directly foreshadowed at the end of The Mandalorian Season 2, when Boba shot Bib Fortuna in Jabba The Hutt's palace. However, the details of his bounty hunting career were still up in the air. Was he going to be the leader of a new bounty hunting organization? Would he use his new position as a way to settle all of his old scores? These were questions that had yet to be answered.
Once the show released, it became clear that Boba was no longer in the bounty hunting business at all. In fact, his motives were to act as a sort of sheriff of Mos Espa, protecting it from invaders and settling disputes between inhabitants. Boba even refers to himself as a "former bounty hunter" to Black Krrsantan. This is a far cry from some other expanded media, which had him continue his bounty hunting ways after escaping the Sarlacc Pit.
1 Boba Is Now An Animal Lover
Perhaps the most surprising new development in The Book of Boba Fett is Boba's new-found love for all sorts of animal-like creatures. Not only does he show affection for the Banthas and Massiffs on more than one occasion while living among the Tuskens, he also shows affection towards his newly acquired pet Rancor (which is not named). He pets and scratches them with glee while they reciprocate his affection in various (and hilarious) ways.
Previous expanded media never showed this side of Boba. In fact, his very first appearance in the Star Wars Holiday Special sees him mistreating the large ichthyodont that he rides upon first meeting Luke and the droids while search for Han Solo. Beyond this, the films only showed Fett displaying affection for the dancers in Jabba's palace in Return of the Jedi.