So this book has been apparently been riding the internets for a few years, but it’s new to me, and a very interesting read. It is at least if you have interest in radio tech, like myself. It starts out with a quite comprehensive overview of radio history (which in itself explains many concepts of the art) and eventually gets into the juicy, technical details — this man knows his stuff. The pdf is called Crystal Sets to Side band, by Frank Harris, K0IYE. You can find it here. I recommend downloading the whole book, and sharing it with any hams you think might be interested, as this is on of the best books on the subject I’ve found, as it wasn’t easily extracted from the noise on the internet.