I've been really enjoying Dark Horse's Magnus Robot Fighter archives. The art by Silver Age great Russ Manning is amazing and the stories hold up pretty good. I love the painted covers a lot of the Gold Key comics had back in those days. I'm not positive these are by Manning but they're beautiful nonetheless.
The pin-ups by Manning are also fantastic. I really like the simple style he used. It was very effective for the subject matter.
If you enjoy Silver Age science fiction comics and haven't read these books, I highly recommend them. It's great stuff.