This "quarterly of speculative fiction," in slightly pricey for the time original paperbacks, was the most experimental, overtly New Wave series of the era. Delany and his poet wife Hacker included poetry, pages of illustrations (e.g. 12 over 20 pages, some erotic, by Russell Fitzgerald, in the first volume), and (also in the first volume) an essay by Delany on critical methods in science fiction. While most contributors were new the field (e.g. an early Gardner Dozois story) there were also veterans like A.E. van Vogt and Larry Niven. Niven's relatively conventional story (in volume four) was the only story to be nominated for a Hugo (or Nebula).

The series was notable for placing author names at the end of each story, rather than below the title, as if to encourage the reader to approach each story without preconceptions. Authors were nevertheless listed on the table of contents--except for volume two, where the TOC was omitted. SFE notes that the series, lasting only four volumes, "sold well, but the hostile critical reaction caused the publisher to close it down."