Lucifer's Hammer by Larry Niven (1983, Paperback, Reissue)

This is one book I come back to over and over when I want something to read. It is so well-written, and there are enough interesting characters, to keep you turning page after page. It has enough science in it to keep it real, but not so much that it bogs down the narrative. You really feel the tension of the characters as they each try to survive and find their way in a totally changed world and find where, if anyplace, they now fit. Great 1980's Pournelle & Niven book that still feels relevant today because it relies more on the characters than on topical references to make its points.