If you're looking for things to read and learn about something, you might find something at the Springer homepage - there's a package of textbooks available that is currently free of charge. The books are mostly introductory books (there's a lot of "principles of" in the titles), and they cover a huge variety of topics. There's little archaeological stuff among them (I found one book about zooarchaeology), but if you always wanted to know things about quantum mechanics, data analysis, programming, machine learning, biomechanics, or social marketing - you might find what you were looking for there.

The books are downloadable both in pdf- and in epup-format. Enjoy!