Way back in the early days of AOL, I belonged to a group that would write short stories and trade them to read on my PC. Ah, the joys of dialup...
The first ebook I purchased was "Between Heaven and Hell" by Jeff Kirvin around 1999 from Peanut Press. I read it on my Palm III. I still remember my joy in realizing I could take my books with me without actually carrying a stack of books!