Can anyone suggest some book-titles that my father might enjoy?

My dad’s been away on business alot, and told me how lonely it gets after the work’s done. I told him to read, and that I rarely get lonely as long as I have my books. The problem is, he really only reads non-fiction, which doesn’t provide the same diversion as good fiction, especially for someone missing loved-ones.
Some of the books I read might not interest a middle-aged business man. I was wondering if you guys could recommend any fiction/sci-fi/thriller/mystery/etc titles he might enjoy? He’s read Dan Brown, if that helps…