Algorithms book, by Jeff Erickson
jeffe.cs.illinois.edu
jeffe.cs.illinois.edu
Think it's being re-posted because it was just published (June 2019), also no more hand drawn photo on the webpage
https://www.amazon.com/dp/1792644833
The text used to only be available via a PDF. Highly recommend if you're learning about algorithms, might buy a copy myself just to support Jeff (and add my own notes into the book).
Term "algorithm" actually comes from his surname because of his works in the field of Mathematics.