is a great reference for hands. It's in a slightly over exaggerated style, which makes it easy to understand how the hands bend. Hands are one of the hardest things to draw.
The other suggestion is to gesture your own hand or find a model. Do them blind. Don't look at the page and just draw the hand, give yourself about 3 minutes and then do another one.
After gesturing it blind, then give yourself permission to do an extended drawing by looking at the page. Use your own hands for references. They're right there.
Here's some examples of gestures where I used a model. This is after years of practicing hands and I still mess them up at times. So it's not an easy thing. The book helps because it has soooo many steps that are hard to break down in one forum post. It really depends on where you are at with drawing hands.