Now it gets a bit more difficult.
THE YUM YUM BOOK, originally done in 1963 and published in 1975 as a hardcover, was not included in the Complete Comics, as the copyright is owned by Crumb's first wife Dana, and she refused Fantagraphics permission to include it.
Scrimshaw Press, 1975
It was reissued as THE BIG YUM YUM BOOK (The Story of Oggie and the Beanstalk).
We think this is an excellent book, although R. himself disavows it somewhat nowadays, calling it juvenile and saying it embarasses him. Don't listen to him.
Don't worry, it's still out there. Try eBay.