Its publication is considered to have brought more serious attention to Crumb's oeuvre, and was one of the earliest attempts to collect a cartoonist's full body of work.
Vol #1 had a revised edition in 2011 to include an additional 66 pages, mostly consisting of the reprint of Arcade #22 (1962).
Even with the expansion of this first volume, it failed to additionally include some of the rarest earliest strips, such as Perry Messin, a 4.5 page MAD comics style parody of the Perry Mason TV show, only found in the fanzine EChhhh!
#3 (Ken Winter publ., 1959) Vol #6 also had a revised edition that appeared in 1997, with an additional 12 pages of material, and the removal of one image that involved Robert Williams.
The first two volumes contain material going back as far as Crumb's teenage years, from before he had had his comics professionally published.