The best video game adaptations add to the world--Bioshock by John Shirley comes to mind, which successfully expanded the story of the rise and fall of Rapture, told in game via audio diaries, but expanded greatly by John Shirley in his adaptation.

This book, rather than asking "If Assassin's Creed 2 were based on a book, what might that book look like?" seems to ask "What if this video game were in book form?" which is a less interesting question.

There is no additional lore or world-building to be gained by this read--it is a bizarrely direct translation of the game to text, in a nearly mission by mission way. As in the game, Ezio even gets a tutorial teaching him the "climbing leap" around the half-way point. There are at least some unintentional moments of humor from this. The modern day/Desmond storyline is left out entirely--understandable due to the level of complexity it's conclusion would add to the narrative, however it also makes the climactic events feel less impactful.

Looking at the descriptions of future books, I have some hope that Bowden's later AC titles are not just direct adaptations of the games, but rather give added depth to off-screen events and characters from them. This one however offers almost nothing but the game's missions in narrative text form.