Classic SF, Fantasy, and Horror
 

Stumbled across this site snooping around for Edmond Hamilton books. If you enjoy older stuff that's hard to find you might find this place interesting. And NO, I'm not affiliated with it in any way (other than my penchant for drooling over great artwork).
http://www.armchairfiction.com/pages/doublenovels.htm

Seen this site before. I was really into Ace Doubles in the 60s and 70s. They published a lot of early work by sf authors from that era. You could find a lot of interesting stuff.