Favorite of all time is too hard to consider.

If you're looking for post-apocalyptic scifi, I enjoyed The Nexus Series and The Silo Series (currently being made into a TV show), but there are probably better books in the genre.

For casual non-fiction reading, the only books I can stand are anthropology or biographies of non-military figures. I've found most of Robert Greene's books enjoyable as each chapter usually has a historical anecdote.