Here's a quick list of books that I've found interesting or useful. And price information is always speculative, at best.
Prices can vary widely from one region to another.
And certain kinds of radios drift up or down in value as various fads grip the collector community. Your public library is another source of technical information. Some of the most useful technical literature has been out of print for years, but may still be lurking in your library's shelves. Fellow collectors are another source of material such as old magazines or technical manuals. This book is invaluable if you're just getting into the hobby, or if you've collected a few treasures but never tried fixing them.