Yes, there are pdf and text file versions of both the Guru book and all the RKRMs (also on the Dev CD) available on the net,but nothing beats a proper printed version to refer to.
I do not believe the Guru book has been included in any online or digital compilation. I have the 1.2 and 2.1 dev CD.
The Guru book was self published by Ralph Babel in limited number. It was not any sort of official Commodore release.
I had been in touch with Ralph a few times over the past couple years about the potential of converting this to PDF.
I think he was contacted by a noteable software developer who has included lots of nostalgic material on the CD of their product too. His response has been that he just didn't have the time to do any sort of conversion or revision of the material.
The original version of the hard copy of this book is 736 pages long with several code snippets tables, etc.
Doing a proper conversion to a digital format would be a daunting task. At this point Ralph still maintains full copyright on his work.
Finding a used printed version is the only option I'm aware of for having this information at this time that I'm aware of.