It used to be available online for free at <https://www.iecc.com/linker/>, but isn't any more. You could get it from archive.org though, and I think I've seen mirrors in other formats on Hacker News in previous discussions about the book.

Yes; but there's also descriptions of legacy container formats no one cares about any more. I still recommend it and have my own copy, I just recall skipping over quite a bit of material.