American Science Fiction: Four Classic Novels 1960-1966 is $2 on
Amazon.com
Collects these novels:
The High Crusade by Poul Anderson
Way Station by Clifford Simak
Flowers for Algernon by Daniel Keyes
And Call Me Conrad (aka
This Immortal) by Roger Zelazny
All, except Zelazny's, were individually on sale in the past.
This is a nice Library of America edition that has many footnotes with clarifications and some background information about the works.