Zenna Henderson is probably the most underrated author in the SF&F field that I can think of. Although her stories are among my favorites, they are long out of print.
Why?
Well, she's deceased (died in 1983), was never very prolific, concentrated on short stories - and had her vision brought to the screen through a movie starring William Shatner, that, by all reports, was pretty bad. (I have avoided watching it.)
Some critics have said they find her work to be "too sentimental" - but I would say, rather, that it is emotionally powerful. She often deals with characters that feel 'different' or disenfranchised, and I have never encountered a writer who could better articulate the longing for something 'more' than this mundane existence... (a common feeling among sf&f fans, I'd say!). She also deals frequently with themes of youth and age, and mixes wistfulness and horror to wonderful effect.
I'd read several of the stories in this collection before, but not all of them. And hey, I have to say that any story that can make me cry not just on first reading - but the third time I've read it as well, has to be pretty effective...
• The Anything Box. 1956
• Subcommittee. 1962
• Something Bright. 1959
• Hush!. 1953
• Food to All Flesh. 1954
• Come On, Wagon!. 1951
• Walking Aunt Daid. 1955
• The Substitute. 1953
• The Grunder. 1953
• Things. 1960
• Turn the Page. 1957
• Stevie and the Dark. 1952
• And a Little Child -. 1959
• The Last Step. 1957