Edit: I reported the issue below, and the author has fixed it.
Note: that will fail on Unix/Linux to get one book, "Systems Programming in Unix/Linux" [1].
The script wants to put the book in a directory named with the book's title, and wants to include the title in the name of the PDF and/or EPUB files. The title includes a "/", which is the directory separator on Unix/Linux, so this does not work out well.
You'll end up with a "Systems Programming in Unix" directory, containing a "Linux" subdirectory, and no PDF or EPUB files.
As far as I can tell, it gets everything else fine.
If you only want PDF files, make this change before running it:
42c42
< links = [x for x in p.links if 'content/pdf' in x or 'download/epub' in x]
---
> links = [x for x in p.links if 'content/pdf' in x]
A PDF only download of everything is 4.5 GB. There are 383 books.