If I can't download OpenResty books from GitBook, I don't see anything.

[Antonio Javier García Martínez]

Hello, 

I'm new to OpenResty and Lua. I've set up a server with Debian 12 + OpenResty, it is awesome. I want to learn LUA and OpenResty, so I've tried to download the book in PDF that should be available here: https://www.gitbook.com/book/openresty/programming-openresty/. However, I can't see anything; it redirects me to my own contents on gitbook. Do I need a paid GitBook account to access the book? I currently have a free account; I discovered the service while searching for the book. 

I have found an HTML version that I can consult (https://openresty.gitbooks.io/programming-openresty/content/), but it's very brief, only covering 'Automated Testing.' Does the PDF version have more content?

Thank you very much! I hope to learn a lot from the list... thanks again.