Envisioned by the husband-and-wife team of Ian and Betty Ballantine, and edited by Lin Carter, it featured cover art by illustrators such as Gervasio Gallardo, Robert LoGrippo, David McCall Johnston, and Bob Pepper. The agreement signed between the Ballantines and Carter on November 22, 1968, launched the project. In addition to the reprints comprising the bulk of the series, some new fantasy works were published as well as a number of original collections and anthologies put together by Carter, and "Imaginary Worlds", his general history of the modern fantasy genre.