I enjoyed this book a lot -- it's quite funny and very clever. I've read other reviews that say that the characters are not very well fleshed out, and that's true, but the plot and the dialog are very strong and worth the read.
As you might have read in other reviews, the plot of "Year Zero" is fairly original -- aliens have been listening to earth music since 1977, and have only recently realized that they have been committing copyright violations on a galactic scale. The protagonist is a copyright lawyer who is working with a group of aliens who want to resolve the legal issues, and they are in a race against time to outmaneuver another group of aliens who would just as soon help earth destroy itself rather than pay the damages. The plot sounds far-fetched -- and it is -- but the book provides reasons for everything that are sufficient to allow most readers to suspend their disbelief.
One also sees frequent comparisons to "Hitchhiker's Guide to the Galaxy" in other reviews of this book. Other than being humorous science fiction, the two books are very different in sensibility and tone. The story is best seen as sort of a saturday-afternoon-popcorn-movie romp with an undertone of social criticism.
As a plus, the audiobook version of this novel is narrated by John Hodgman, the PC guy from the "I'm a Mac, I'm a PC" macintosh commercials and commentator on The Daily Show with John Stewart.