I will second your recommendation on Rich's new book, ash! This book is really the "Bible" of reference works on the music of Peter Green and it will be for many years. Rich has been working on this for a long time, and a lot of us have "met" him here on The Ledge over the years.
There is nothing else that's ever been published like his new 3-volume work. Amazingly detailed descriptions of the music as well as information about early Fleetwood Mac (and the Bluesbreakers) and its members, their influences, and contemporaries. Overall the focus is squarely on the music itself, and as ash mentioned, it covers every known recording involving Peter Green that has survived - studio recordings and out-takes, BBC sessions, and both professional recordings and bootlegs from live shows.
A quick note that Rich has published the book through his own Smiling Corgi Press, and so far I believe it is only available directly through that website - here is the page for more detailed info and for ordering (it's available as an e-book as well as paperback):
https://smilingcorgipress.com/shop/
I should also note the fantastic blog that Rich has on his Smiling Corgi site - lots of great posts related to Fleetwood Mac and related blues artists:
https://smilingcorgipress.com/blog/
If you're interested in reading about the music of Peter Green and early Fleetwood Mac, Rich's book is definitely for you!