If you ever wanted to read the 1st issue

CGC Certification Verification (http://www.cgccomics.com/1134755001/#features/)

The really cool thing about this isn't so much that its Superman's first issue (actually Action Comics #1 and not Superman #1), but that its a high quality scan of an original, physical issue from 1938 including the old ads and the stories other than Superman included in pristine condition.