It is - apparently, it's open source and they can do this without paying royalties amazingly. There are many others in the series....
Coincidence - I was looking for stuff on comedy singer Allan Sherman a couple of hours ago and noticed one of these for parody singers, including Sherman, Neil Innes and 'Weird' Al Yankovic. I thought - that looks an interesting book, but couldn't find any more info on it anywhere on the web. Now I have my answer, so thanks for raising that question, Gub.
Jules