It's taken me nearly a year to actually get around to finishing this, so unfortunately I can't really remember the details of every short story. I do know I've enjoyed reading this, and I'm looking forward to reading the next one. Bellow are the notes of each story I took after reading.

Time Quarry by Clifford D. Simak
gripping mystery, details revealed in a good way, characters are a bit blank but liable enough. Can tell there's more to explore in the world/story, makes you very excited to read next part

Third from the Sun by Richard Matheson
Very suspenseful, interesting premise, with a fab twist at the end.

The Stars Are the Styx by Theodore Sturgeon
amazing main character - secondary characters a bit meh, but great world building and story

Later Than you Think by Fritz Leiber
Twist is given away by the tag line -
BUT THEN NOT! RATS!

Contagion by Katherine MacLean
Interesting twist - not really enough time spent on the implications imo

The Last Martian by Fredric Brown
a bit lack luster - another interesting twist at the end

Darwinian Pool Room by Isaac Asimov
Sci-fi version of Plato's Republic. Ended just before it got boring to keep reading. ( )