Konstantinov Andrey has created a very handy tool to create JAR eBooks named mjBookMaker. Comparing with TequilaCat or ReadManiac, I've found it simpler. It's ideal for reading books on any java enabled mobile phone that does not support PDF readers. I didn't find a place to thank him on his page so I would like to leave a comment here to say: "Thanks konstantinov" ;-).
I addition, ManyBooks is an interesting place to find free books. It even has a on-site conversion tool that enables the user to download books in a variety of formats like JAR files (Actually I found mjBook link there). Thanks to the founder ;-)