Humble Bundle sometimes has bundles of technical books. The bundles are available for two weeks each, but once you buy it you have them to keep. Currently (as of 3/12/2018) they have a bundle of A.I. eBooks. They range from coding an AI for playing games to implementing Deep Learning for Computer Vision. If you have an interest in Machine Learning or Artificial Intelligence at all then you might want to spend the $15 to pick up the whole bundle.
I did and I think Jason did
I did pick it up and I’m getting a lot out of it so far. I like the Machine Learning Algorithms book as an intro to the field.
They just put up another bundle today for DIY Electronics that some people here might also be interested in. It has some books on Arduino, Raspberry Pi, Beaglebone, and basic electronics.