"As True to Mass Effect as You Can Get"
I haven't listened to a whole lot of audiobooks yet - only 5 or so - but Mass Effect is at the front of the list.
If you're a fan of Mass Effect, you can't get much better than Drew Karpyshyn - the lead writer of Mass Effect 1 and 2. His style and attention to world building - without turning into an encyclopedia - translates the feel and universe of the game very well. It's impossible to write a book about Shepard, but David Anderson makes a great analog, and fun - if predictable - character to follow.
I was spoiled after listening to Star Wars: The Old Republic: Revan with it's dramatic reading, music, and sound effects; I was mildly disappointed that Revelation did not have those things. I wasn't disappointed for long. David Colacci does a fantastic job, and while he doesn't strive to copy exactly the voices of characters like Anderson and Saren as they're heard in the game, he copies enough of their inflection and style of speech that you buy it early on.
All-in-all, a great book for any fan of the Mass Effect games. You'll learn more about some key characters and their past, flesh out more of the universe, and expand your understanding of the overarching story of the games. I definitely recommend it.