Birkley Breathed's Bloom County was my two favorite comic strips growing up, and now it's starting to become available in iBooks. From Bill the Cat's run for president to Milo's skewering of Senator Bedfellow to Oliver's landing the space shuttle to Opus'... everything, it delighted me on a daily basis.
The iBook's implementation isn't ideal, at least in my brief skim-through -- the pages don't turn as easily as a regular iBook and instead the double page spread slides and flops, and only the first three volumes are currently available, but I applaud them getting it into the iBookstore to begin with and look forward to the whole series.
Hopefully Bill Watterson's Calvin and Hobbes, my other favorite, will join it in iBooks soon. (Like Bloom County, I bought the complete series the day it went on sale but would dearly love it in digital form as well.)
Adorn your shelf with it now.