Hi Jamie. Maybe 50% of the songs (which as you probably know are all from the first three LPs) have some kind of tab - sometimes an intro, sometimes a suggested picking pattern, sometimes a short break or harmony line within the song. There are also explanations of alternative tunings (quite a few) and non-standard chord shapes. Things like 'Minotaur's Sing' and 'A Very Cellular Song' have keyboard arrangements as per the recorded versions. There are no songs with a complete tab from beginning to end, so you have to do some work yourself.

From his intro I'd guess that Happy Traum used his ears to work them out, though I suppose RW might have given him some tips on the tunings. It's a few decades since I tried to work out those guitar parts and I'd say that, while not always re-creating the sound of the record 100% accurately (bearing in mind I listened to those LPs obsessively and knew every note!), they get pretty close in most cases. It looks like Traum took a lot of trouble over the book.