I originally purchased Sabrina Mesko's book Healing Mudras, but I was very disappointed. As much as I wanted to learn about mudras, I found the book annoying to read due to the layout, font choices (lots of italics) and red-colored print. I also found the mudras impossible to decipher from the photographs. So, with much disappointment, I put the book on the shelf along with others that collect dust. Then I discovered Gertrud Hirschi's book Mudras: Yoga in Your Hands, and I was thrilled. This book is so comprehensive but easy to read. The text is clear (black on white), the meditations are fantastic (and there is an incredible array to select from), and the line drawings are simple, direct, and very understandable. I was able to immediately dive in and make good use of the countless mudras and meditations. There are even mudras included to assist with healing physical ailments. I was highly skeptical of these from the outset, but I tried the bronchial mudra, and to my enormous surprise (and delight!), I was able to forego my allergy medication and could breathe freely through the night.
If you want the BEST book on mudras -- with a lifetime of exercises and meditations -- THIS is the one to get. It's clear, concise, and complete, and an absolute joy to read and use.