My first Assassin's Creed novel was Forsaken and perhaps reading that one first set the bar a little high. Oliver Bowden seemed comfortable and free in that environment and in a way he was, since Haytham Kenway was still somewhat of a mystery after the AC3 game proper. I acknowledge that because the events in Revelations were already played out in-game, the author had very little leeway to create something new. That said, there are still a few things that I found wanting in the book overall.
Even though Revelations takes place primarily in the sights and sounds of Istanbul, I found that the framework was surprisingly lacking. The book takes place in a location that, even today, sparks the imagination with culture and wonder. In the game, I felt as if Istanbul itself was a living, breathing character around Ezio, unique and all its own. The book, conversely, spent very little time on the setting, which surprised me. I was also surprised by the utter lack of new story or even narrative flow in this book. It felt almost mechanical at times. In my head, rather than picturing the events taking place in the book I was reading, I was picturing the author playing the game, pressing pause, and writing down what he'd just done on the screen. The effect is that events and dialogue feel choppy in a lot of places where central story should have flown easily. Because of the choppy narrative, Ezio suffers as a character too. Book Ezio never seems to have that certain charisma that the in-game character had in excess.
The bottom line is that the book was a good way for me to pass a long wait in an airport, but if you've played the game, this book will not add any story elements or intriguing new thoughts to the Assassin's Creed universe.