The Conjuring Arts Research Center (http://conjuringarts.org/) is having an e-book sale, in addition to the free e-books they are giving away as posted earlier here.
The sale is 15% off your first e-book, and 30% any subsequent e-books. When I tried to pay by Paypal, the discount didn't show, so you might want to use a credit card if you purchase. It may be that if you clicked through the purchase that the discount would show, but I didn't take the chance. Paypal can be weird, sometimes.
The catalog is huge, so I've created a Google Docs spreadsheet that lists all of the e-books (current as of the 2nd of January) by Author, Title, Price, Pages, and Description, along with a block so you can check of the books you already own.
The catalog is available at: https://docs.google.com/spreadsheets/d/1Klaqp8ghCS7jDFdUHoc1VTFm2jCFT96aJ3XfXO526hk/edit#gid=875139125
You can download it and then edit it locally for your own use.
I have no affiliation with Conjuring Arts; I just put together the spreadsheet for my own use and thought others might find it helpful as well.