I enjoy helping individuals educate themselves. In pursuit of this goal I try to find sources of free educational material and share them with as many people as possible. Recently I stumbled across the Open Culture website, which has a page listing freely available textbooks.
I haven’t had an opportunity to dig through all of the listed textbooks nor am I qualified to determine the accuracy of the material in many of the listed books. However, of the few textbooks I have perused, they appear to be good quality and were written by credentialed professors.
Feel free to go through the list and download anything that piques your interest.