Superman paperback series -- name?

[Validus]

I am trying to recall the name of a certain series of superman books from the early eighties.  They were small softcover books similar in size to the Adventure comic books at the end of their run in 1983.  

Each issue included several stories that were reprints of old issues, revolving around a particular theme.  One was all about kryptonite, and had stories involving each type of kryptonite.  Another focused on Lex Luthor.  Another was about superman's most powerful opponents, and had stories of superman against Solomon Grundy, the Sand Superman, Vartox, and the Parasite.  Another featured stories about Krypton.  These are the four that I remember, but I know that there were others.  

Does anyone recall the name of this series?

[nightwing]

Sounds like you're remembering the old "digest" sized reprints.  This was a popular format for a while, and in fact Archie and maybe some Harvey titles are still published this way (look for them in the check out lines at your local grocery store).

Anyway, the ones you mention were probably part of the "Best of DC" line, also known at times as "DC Blue Ribbon Digest".

Here's some covers...

http://comics.org/covers.lasso?SeriesID=2493