Dana Stabenow's Kate Shugak series is great. "Breakup" and "Blood Will Tell" are possibly the best in the series, but that's comparing excellence and excellence.

If you REALLY want to think, read "Godel, Escher, Bach: an eternal golden braid." It's nonfiction, but I'm not going to even attempt to explain more about it.

Or read up on Chaos theory. Or the 14th Century. DON'T read (very much) in your usual fields of work.

Also, have you considered using the time to learn a new instrument?