Drawing Dynamic Hands is a really good book on drawing hands. It explains almost everything you need from the form, structures, proportions, anatomical landmarks, functions to foreshortening. The illustrated examples are plentiful with hands in almost every humanly possible pose. There are so many to practice from.
The only problem with this book is the ridiculously muscular fingers in all the examples. We don't see this level of muscles even in superhero comics. But you already know that when you buy a Hogarth book.
This book is perfect for anyone who wants to draw hands. A general anatomy reference book is recommended as companion for those who cannot get pass the over stylized Hogarth style.
(There are more pictures of the book on my blog. Just visit my Amazon profile for the link.)