Erwin Puts is working on a new 500 pages book called Leica Practicum that will start shipping in April and will be priced around EUR65 (incl. shipping). His books are usually limited editions and are hard to find which also drives the price up (see the current listing on Amazon US, Amazon DE and eBay). From his blog post:
"As you can glean from the content overview below, the book covers much new ground, that has never been discussed in the Leica world and almost never in the general world of photography. I am convinced that this information is necessary for a true assessment of the state and future of Leica photography and its practice. Theories of Photography are a theme that is hardly ever discussed in the Leica world, even when many Leica photographers have made comments about this topic. In this book I discuss the typical style of Leica rangefinder photography (snapshots, street photography and documentary photography) and analyze the characteristics and limits of this style. I discuss some guidelines for a genuine theory and philosophy of Leica photography that is applicable for analog and digital photography."
You can see the table of content here.