Structure and Interpretation of Computer Programs (SICP) by Abelson & Sussman.
Already available from MIT Press for free, SICP is available here with newly typeset mathematics and figures.
You will find Kindle versions as well.
A truly remarkable addition to e-texts in computer science would be TAOCP. Somehow I don’t think that is going to happen anytime soon.
I first saw this in a tweet by thattommyhall.