This is a classic. It is the first book of its kind, and probably the first book about Star Trek at all. But The Making of Star Trek is much more than any of the later books with similar names. This book doesn't idealize or simplify the making of the series. It doesn't enthusiastically praise everything and everyone involved in its production. It is an authentic and meticulous report on how TOS in particular and a TV series in general comes to life. It shows that it is a process of try and error, that aspects have to be taken into account the viewers wouldn't think of, and that the responsible persons don't always know exactly what they want ("I need some device that does something...").
The story how Stephen E. Whitfield (aka Stephen E. Poe) asked Gene Roddenberry if he could write a book about the series sounds like a fairy tale, but is true. The Great Bird was very forthcoming, and Whitfield was granted access to everything behind the scenes of the still running show, seemingly without any restriction. The book shows production schedules, budgets, private notes, script drafts, production sketches, all things that are usually kept secret or simplified for a larger public. I don't think that something like this would be still possible today. Compared to The Making of Star Trek, Whitfield's last book (he passed away in 2000) on Voyager seems rather superficial.
The Making of Star Trek may be over 30 years old, but it is of more than only historical value. It demonstrates that TV is a business that sometimes doesn't allow technical or artistic perfection. It also shows how many things we may take for granted and that are essential parts of the Star Trek Universe today have taken a rather surprising course change. Who would like Vulcans with names like "Spook, Spork, Splak, ..." as frequently suggested in the early days, or who would think that one race was originally described with the words, "Honor is a despicable trait.", namely the Klingons?