Name of a series of children's science fiction books from the 1970s - not set in same universe / not sequels

Question

In a public school in Mississippi around 1977 I came across a series of science fiction juvenile books. When I say "series", I mean that they were by the same publisher and had the same binding...but they did not share characters or setting or plot. The books may have been fairly short (30 pages? 100?)

One book was about people living in an underground city who ventured to the surface and found that the apocalypse that had caused their ancestors to tunnel down was not nuclear war, but vast mountains of garbage (no, this is not "This Time of Darkness" by H M Hoover!)

Another was about astronauts who land on a planet. While wearing space suits they encounter a woman who walks around suitless. She convinces one of them to take off his helmet because "the air is fine". He does, and dies. It turns out that she is actually some sort of alien energy vampire who feeds on his death.

Answer 1

The Space Science Fiction Series (1970-1976) by Benetic Press (and another press whose name escapes me) was shelved interspersed together at my Elementary School library. They all shared the same binding and artwork covers however. One of the imprints by Benetic press included the authors Henry Bamman, William, Odell, and Robert Whitehead. Bamman authored or coauthored most of the works in this series including Milky Way, Bone People, Ice Men of Rime, Planet of the Whistlers, Inviso Man, and Space Pirates. I could not find the titles to the other books from the other publisher with the same size and cover artwork. The story about the energy vampire rings a bell and is perhaps "Ice Men of Rime" or "Planet of the Whistlers." I hope this will help take you closer to your search.