"Theremin: ETHER MUSIC AND ESPIONAGE" by Albert Glinsky
I finished it a couple of days ago. There aren't too many of these types of books, and I don't mean to in any way dump on the author, but comparing it to the book on Hugh Le Caine ("The Sackbut Blues: Hugh Le Caine, Pioneer in Electronic Music" by Gayle Young) there is perhaps too much (related and unrelated) historical background, and too little focus on the book's subject - particularly from a technical angle. I would have liked at least a brief appendix covering the musical instruments Theremin designed. Pictures, and ideally schematics (if available) and some technical depth on what we know about each of his designs would have been awesome. I also got the feeling the author's meeting with Theremin in his 90's dotage perhaps made too strong an impression on the author.
It was an interesting read though, and I'm glad the book exists.
[EDIT] I should add that there are three sections of pictures in the book, and many of Theremin's instruments are shown there. And there is some discussion of the instruments in the text. I think a dedicated appendix or chapter on the instruments themselves would have been nice.