In August, 1966, Stephen E. Whitfield, then in the employ of an advertising agency, was tasked with working to generate publicity for Star Trek toys. In consequence of his close contact with the Trek cast and crew, he became intimately familiar with the workings of the production, and pitched to Gene Roddenberry a book detailing the making of the show. With Roddenberry's approval, Whitfield began work on what was to be a thorough history of Star Trek, from its conception through the production of its first season: The Making of Star Trek.

Whitfield's book was the first of its kind: a real behind-the-scenes look at the creation of a television show, including not only Whitfield's observations, but also interviews with Roddenberry and the actors, and original artifacts from the show's production, such as the 'series format' Roddenberry wrote to sell the show to the studio, and a variety of memos.

The aforementioned series format is perhaps the single feature of greatest historical interest, as it describes Roddenberry's initial vision for the show. In part:

The book features a great many more original documents from the show's production that will be similarly interesting to the devoted fan. It's well worth reading for those.

Of rather less interest (to me, at the least) are the minutiae of the show's production. In 1968, I suppose the work of making a television show was relatively unfamiliar to the average person. Today, I think this information has permeated the collective public consciousness, and at any rate the internet will offer (up-to-date!) details to anyone interested. Happily, these duller bits are in the minority.

The Making of Star Trek is an absolute treasure for the fan interested in Trek's history. I understand that many of these details have been republished, since, but Whitfield's book is the only source written even as the show was produced, and published contemporarily. It's well worth the time invested to read it.