Rigan Michado, one of the most knowledgeable Brazilian jiu jitsu practitioners in the world, introduced for the first time in published form his famous "Machado Jiu Jitsu" techniques. This book encompasses an enormous variety of techniques, including arm locks, chokes and leg locks.
This is a really quick read… well, I say “read” when what it mostly boils down to is looking at pictures. The (very short) introduction reads more like an ad for the Machados, followed by a very basic overview of the main techniques of jiu-jitsu. One plus is that they included plenty of leglocks, and there is a whole separate section for no-gi variants of techniques. However, the stuff shown is either already familiar to anyone who trains, or lacks enough detail for a non-trained person to fully and correctly implement the techniques. This may have been the underlying idea – to get people to try stuff, fail and/or see that once you actually physically try this stuff it comes off kinda sloppy, and then seek an actual academy where they could learn all the tiny tweaks that make the techniques truly effective.
I liked this. While the photos and directions aren't always that clear (and on one technique the wrong photo was put for the finish), it was a good book with a clear and soundly articulated training philosophy.