The Mote in God's Eye, by Larry Niven and Jerry Pournelle
Larry Niven is easily my favorite science fiction author, so I tend to shy away from book he's written with another author. This book, although I thoroughly enjoyed it, reminded me why I do so: What I love so much about Niven's writing is how funny it is, and while this book definitely has funny parts, they're just not quite as good as his solo work. Granted, the subject matter is pretty heavy - first encounters with intelligent alien life and the possibility of government-approved genocide - but Niven has dealt with very serious subjects before and they are always presented with humor. That being said I really liked this book; it pulled me in just like any other Niven work and the science is sound, something a lot of science fiction lacks. I'd be curious to read something by Pournelle to see just how much each writer's voice informed the writing.