Once upon a time there was a world without the internet. In those days tracking down Trekkies could be quite a struggle. Turnbull's book was a great tool.
He provided a write-up of a visit to a Star Trek convention, an episode guide, and listings of fan clubs by state.
I actually found a groovy fan club using this book.
Nice writing, great illustrations by fans, and lots of photos. This book is a highly recommended blast from the Trek past.