Packt is having a sale. The book is $10. That is an insanely low price and no DRM so it works on any e-reader. For $10 you get all three formats ePub, Kindel and PDF. (a paper version costs more, if you want that)
I have a copy. This is one of the best books out there.
(no connection with publisher or author, just wanted people-to know about the reduced price.)