Ask HN: How to preserve webpages locally for later reading?

I wanted to write a little script to preserve webpages at URLs for later reading, and I was wondering what was the most high fidelity and space-saving way to do this. Sometimes I save pages as PDFs to get that kind of fidelity, other times I save them as HTML. The problem is sometimes when I save pages as HTML you get the actual page and this folder structure that I don't really understand.

Is the save-as-HTML option more high fidelity? And if so where can I go to understand the structure of what I download?

EDIT: Thanks for the pointers, they're very helpful. I'll use HTTrack for anything wget breaks on.