You don't _have_ to get an Eink device. There are a number of cheap tablets on Ebay. I have the following, and it's pretty good with PDFs:
discussion
https://www.mobileread.com/forums/sho...427#post294427
legacy support site:
http://www.la.viewsonic.com/support/...l100/#features
ebay auction:
http://search.ebay.com/airpanel-100_...dsreturnedZ300
I'm getting at least 5 hours battery life.