Analog Devices has recently released a new 375 page textbook for free called 'Software-Defined Radio for Engineers, 2018'

The RTL-SDR site says this is an advanced university-level textbook that covers communication systems theory as well as software-defined radio theory and practice.

The book uses the PlutoSDR as reference hardware and for practical examples. The PlutoSDR is Analog Devices $150 RX/TX capable SDR that was released about a year ago.

RTL-SDR - https://www.rtl-sdr.com/software-defined-radio-for-engineers-free-university-level-text-book-with-plutosdr-examples/

Download Free book SDR (PDF) - http://www.analog.com/media/en/training-seminars/design-handbooks/Software-Defined-Radio-for-Engineers-2018/SDR4Engineers.pdf