The whole title "The Book of Boba Fett" made me think that the story would largely be about how did Boba Fett eventually wind up on that throne at the end of season 2 of The Mandalorian. I think the big question might be just how far back might things go?
Recently I was thinking this - could this show be a way to bring some of the stories for the canceled Star Wars - 1313 game and the Star Wars Underworld series to light? One thing that Star Wars creators have not been shy about in the post GL era is mining past material for new projects - Ralph McQuarrie concept art being revisited in numerous ways, the concept of the Temple of the Whills in Rogue One, Mimban (location from Splinter of the Mind's Eye), the Bendu, etc. So why not mine something that George Lucas had his hands in like 1313 and Underworld? Some reports indicated that 40+ scripts for Underworld were written before the project was shelved. I think the possibility of this happening could be rather high, as Kathleen Kennedy said in 2015 that material for both the game and the show might be developed further for future projects.
I think that the events between ROTJ and The Mandalorian seem almost obvious for this series. And I recall seeing some passing comments lately that some big OT actors might come into play in future projects. This show seems like it could be one of those, and that sort of thing seems to be on the table after seeing the season 2 finale of The Mandalorian. Lucasfilm seems to be taking the possibility of incorporating legacy characters into new shows very seriously, and I saw another news item that said LFL has hired a person who has made some absolutely amazing deepfake videos of Star Wars material - they did improved versions of Tarkin and Leia in Rogue One, and a better version of Luke in The Mandalorian.
To me so much could be on the table for this show. I don't think we're going to have a clue about where this Boba Fett series goes until we see a trailer.