Hi! I've spent 10 years reading books on my Palm units, the latest being a Tungsten T3. It's great to have a book in your pocket while waiting in the grocery line!
http://www.ereader.com has a format of books for the Palm, if you don't mind buying the books. Their free reader works on the Palm, your PC or your Mac, and other handheld units too. And so does mobireader, which you are already familiar with. Enjoy!!