At the time I had a lot of Ebook's on my computer (Baen, PG, etc) but reading for hours on the computer just wasn't that comfortable.
So I wanted a small device that could go where I went, be it my comfy chair in the living room or my fishing chair down by the river.
That is what got me hooked.
What has kept me hooked is vast #'s of books that fit on 2 gig SD cards, being able to read anytime, anywhere with just a push of a button. Since then we are up to a 4 ebook reader family, and my wife is planning on giving her boss one for Christmas.
The only thing that could be any better would be a direct book reader to mind interface.
I figure by the time my eye's are worn out we'll have it.