This is Groff Conklin's fourth anthology, and it was published originally in 1952. It contains 43 stories, 22 of them from 1950-1952, and the rest from the 40's, 30's and 20's, and one by Jack London from 1912. As one might expect, with the surge in number of anthologies in this period, they draw more and more on the stories which were published more recently.
Two of these stories have been nominated for Retro Hugos: "What You Need" by Lewis Padgett was nominated in 1996 for the Retro Hugo for Short Stories written in 1945, while "A Subway Named Mobius" by A. J. Deutsch was nominated in 2001 for the Retro Hugo for Short Stories written in 1950. In addition "The Colour Out Of Space" by H. P. Lovecraft is included, which tied for 12th on the Astounding/Analog All-Time Poll in 1971 for stories written before 1940, and tied for 26th on the Locus All-Time Poll for Novelettes in 1999.
Other noteworthy stories include Jack London's "The Scarlet Plague", and end of civilization story, André Maurois' "The War Against The Moon", Ann Griffith's "Zeritsky's Law, and many others. While this collection is not as strong as the previous ones, it is still a very good collection of stories. This is definitely worth picking up if you have the chance and enjoy early science fiction.