Having just finished two of Farmer's series (World of Tiers and Riverworld), I'm ready for more. The Dayworld series is a bit shorter (3 books) but it's the strangest. It takes place far in the future and there are 7 different governments, one for each day. One seventh of the population is active each day, so less than 2 billion people are using resources per day. The major crime is called 'daybreaking' and it's when one tries to live on a different day. The protagonist is, naturally, a daybreaker and assumes 7 different lives. It's stressful to read and I imagine it was hell to write. Often, we hear of double agents or even triple agents, but imagine a septuple (is that the right word?) agent.

Hey, that actually sounds pretty cool.
If I weren't insanely busy with all the other stuff I have to read, I'd try this out.