Do you need The R. Crumb Handbook by R. Crumb and Peter Poplaski? Well, yes and no. For total, 100% completeness there are a number of pictures in here we don't seem to have anywhere else in our Crumb Collection. Plus there are lots of photos and Crumb bio info. There are several essential strips (also in the Complete Comics), as well as relevant non-Crumb source material (Pogo, etc.).
And then there's the free CD of Crumb playing his music!
The Limited Edition
Apparently with the limited edition you get a print but no CD.
This book was the "catalog" available at the Crumb exhibition that toured art galleries across the world c. 2005.
Exhibition poster from Rotterdam, the Netherlands