Alongside the two issue mini-series, a Portfolio was produced intended to showcase not only the characters of the DCU, but some of the artists most associated with them or, in a few cases, previews of what was coming up.
Perhaps most interesting among them is John Byrne’s Freaks, a series that was pitched but was never published at DC. Some of the ideas and characters would influence later series of his at other publishers, as per this article.
HISTORY OF THE DC UNIVERSE Homepage
Crisis on Earth-Prime 