For exquisite Ace Books trash, there's nothing that can top the Perry Rhodan series. This was my first serious SF fandom -- I stumbled into the books about the same time my local station finished a run of Star Trek in the after school time slot, and replaced it with Wild, Wild West. WWW was OK, but it didn't scratch my 12-year-old sense of wonder.
So I started reading the Ace edition of Perry Rhodan, edited by Forry Ackerman and translated from the German by his wife, Wendayne. That was more like it! I'm afraid to try and re-read them today, for fear the Suck Fairy has visited. But yeah, for the rest of my teens, I was into PR fandom, even publishing a dittoed fanzine for a couple years when I was 15-16 or so.
Astoundingly, Perry Rhodan is still going strong in Germany, coming out with a new 30,000 word novella (published as a booklet) EVERY WEEK! The series started in 1961, so they must be well over 3000 issues by now. In the US, we didn't even get to #150.
Our West German correspondent, Cora Buhlert, has been doing a lovely job of describing/reviewing the Perry Rhodan novels!
http://galacticjourney.org/tag/perry-rhodan/