Comment by Lukey on The Best Textbooks on Every Subject · 2019-03-16T16:28:47.417Z · LW · GW

I don't have any recommendations yet, but want to note that some Books can be read and downloaded at archive.org, for example Spivak's Calculus: https://archive.org/details/Calculus_643. For some Books you'll have to sign up to "loan" a Book Online.