The new book is out. It's a concise low-math (almost zero math) description of what SDR (software defined radio) is all about, for the general ham radio audience.
The short message: It's the main technology at the core of about every HF radio you can buy these days. If a radio has "IF DSP" it normally has an SDR back end. Front ends vary, from minimal ("pure" SDR) to conventional, but the digitization and digital signal processing is mostly the same.