How can I tell what edition a particular Shadowrun book is for?
Check the Back
Unlike some publishers, where you frequently have to examine trade dress and other elements of the book's design, Shadowrun's publishers - FASA, FanPro, and Catalyst - have been good about including the edition's name in print on the back cover. Sometimes it's a standalone line "For use with Shadowrun [Edition]", while other times it's in the body text of the back cover blurb itself. They even call out when a book straddled multiple editions, most often seen during the transition from SR1 to SR2:
This is not to say that they don't have trade dress that they change up with each edition, but reading the text on the back doesn't require remembering which color scheme is which edition.