I'll be as unbiased as I can. I like the book, only because I'm a hardcore Assassin's Creed fan, so that is why I gave it a three, which is already generous because it
leans more closer to a two star novel. As a book fan I would only give this one or two stars. Here's why.
The story of the first game and Bloodlines is retold and it is interesting to read it, seeing how everything connects in the first game in a cycle that is repetitive, but not as repetitive as in the game, cause the author manages to bring some variety to it, but this could have been done much better. The story is not very descriptive, it just mainly repeats events, conversations from the game. It lacks describtion of the locations of the characters in general, which makes them lack depth. It's not worse as the first game, but with the oppertunity to create this novel, he could have really added more depth. Yes he did not manage to do this. It's mostly just all directly from the game. (Minor spoiler ahead) Mostly I misssed the conversations Altaïr has with Malik as his character really shows, and how it shows how he slowly changes, not just jumps from one point to the other.
When we get to the part of Bloodlines it gets a little better, but I don't think this is because of the author's writing, but because the game itself didn't have a story where this cycle just repeated itself (assassination, back to Masyaf, assassination, back to Masyaf and so on...). That is what made this part more readable, but again I don't think we owe that to the author. Once again he isn't very descriptive and could have added much more to the relationship between Maria and Altaïr.
The only good thing I can add is that between the events of first game and Bloodlines there are a few scenes of Altaïr's younger life, which is kind of a build up for what happens in his later life. It's third part where it at least got more interesting, where the stories of Altaïr's begin, but while it is interesting to read what happened afterwards, you do once again get the impression that it could have been done a lot better. What you miss were more personal conversations again with Maria and Altaïr and other characters. The over all story of the book never really gets very personal.
For Hardcore Assassin's Creed fans who want to know as much as possible it might be worth it to buy this book. But I wouldn't recommend it to others.