Just in case you might be interested, today only (Monday Dec 13), O'Reilly Media has all of their Pocket Reference Guide Ebooks on sale for $3.99! The link is below, and when you get to that page, there is a link to see more pocket guide ebooks as well.
Use discount code DD399 in the shopping cartI think I'm going to get a few. They aren't the full textbooks, but rather that pocket guides. Still...for $3.99 each for ebooks that don't take up any room on your bookshelf that I can read on my computer or my ereader?
NAYY (No affiliation, yada yada) Just passing on an opportunity.