pamela
Video game tie-in novels can be very hit or miss. I was pleasantly surprised by Mass Effect: Revelation as it was not only a great introduction to the Mass Effect universe, but it was also a pretty fun read.
Mass Effect: Revelation couldn't stand on its own as a piece of science-fiction. While it gives a good introduction to some of the Mass Effect series' characters, its races, and Citadel politics, it doesn't do much world-building beyond that. It's a book created for people already interested in the series, and with that in mind, it does its job wonderfully. Having already played the series multiple times, reading Mass Effect: Revelation gave me a much deeper insight into the characters of Anderson and Saren.
Mass Effect: Revelation is a video game prequel and it does what it says on the tin. If you're interested in the world and lore of Mass Effect, then this is a really fun, well-written read.