Best manual for technique - will shoot quality of your espresso through the roof with simple explanations of all the techniques used to make espresso and milk drinks, as well as why you should do them.
Negative Product Points
Schomer is pretty much the most anal person about coffee in the world. I think it's absolutely hilarious when he goes into such details as brew temp range. But, he's also pretty much the most respected voice in coffee in the world, so it's okay.
David Schomer's book is by far the best guide to improving your espresso preperation technique. He covers topics such as dosing, distributing, tamping, temperature, roast degree, grinding, frothing milk, pouring art, etc.
By far, his manual of espresso has been the largest improvement of my technique since I got a pump espresso machine. Simple, minute changes in technique produce quality in the cup that is incomparable. The main one I gathered from his book is tapping the side of the portafilter just once. HUGE difference.
Of course, this book is "professional techniques" so some of his advice really can't apply to the home situation. Namely, his espresso temperature belief. He says his espresso blend is best in a 1 degree band of 203.5-204.5 degrees fahrenheit. This won't work in the home, but if you own a Synesso or LM Linea, it will obviously be good advice.