Advent:Publishers

Advent:Publishers is an American publishing house. It was founded by Earl Kemp and other members of the University of Chicago Science Fiction Club, including Sidney Coleman, in 1955, to publish criticism, history, and bibliography of the science fiction field, beginning with Damon Knight's In Search of Wonder. With books like In Search of Wonder and James Blish's The Issue at Hand, Advent became the genre's first scholarly publisher.

From the Wikipedia article “Advent:Publishers”, licensed under CC BY-SA 4.0.

Large trade publishers generally accept manuscripts only through literary agents, while many independent and small presses accept direct submissions during reading periods. Before submitting anywhere, read the publisher's current guidelines, study recent books on its list, and never pay a reading or publishing fee to a traditional publisher.