I was blessed to receive an e-book reader for my birthday (and Christmas, etc.). It's really great. And I have a tendency toward fantastic fiction (lately it's been David Weber), but I try to temper that with some reading that's good for me, and not just junk food.
I found out Crossway was offering the ESV Study Bible in EPUB format for $15, and decided to get that. The nice thing about the electronic version is that if you choose to ignore the footnotes, you've got a regular Bible for reading, something you absolutely can't do with the print version of the thing.
Better yet, it turns out that my favorite ebookstore for fiction also carries a whole bunch of Crossway books. Who knew?
Fictionwise has 130 titles available from Crossway. They are distributed in multiple formats (abbreviated multiformat on the site), which basically means that any reader you have you can download a version of the book for it. You can download in one format, or several. Not only that, but through the end of this week, all of those books are 40%-60% off. So instead of paying $10.00 for Mark Dever's "The Message of the New Testament: Promises Kept," I paid $4.00.
In fact, I think most of the Crossway books are $4.00. Here's the link to a list of Crossway books on the site.
I don't know whether their week ends on Saturday or Sunday, so you'll have to act quickly.
P.S. They've also got Tim Challies book there. Don't know if I'll be getting it this time around, but it's nice to know it's available electronically.