Of all the art technique books I've ever looked at, this has been one of the most useful to me. Graphite is and always has been my favorite medium for drawing, and though I've tried others, I always find myself falling back on the trusty generic pencil. So when I saw this book in the store, I picked it up and thumbed through it and was so impressed by the author's example drawings alone that I bought it. The author is a magnificent artist, and the book has turned out to be a great reference. I've noticed a marked improvement in the realism of my drawings since I started using it.
Hillberry begins by introducing us to various materials - graphite pencils, charcoal pencils, carbon pencils, types of erasers, blending tools, types of paper, and other miscellaneous items that can prove helpful - and describes the use and effect of each. He goes on to offer tips on choosing a composition, using light for different effects, using different pencil strokes, blending techniques, layering media, masking, and other helpful methods.
The bulk of the book contains instructions on achieving realism when rendering different types of objects: metal, eyes, human hair, glass, broken glass, wood, leather, barbed wire, clothing, and fur. He even offers instructions on little details such as knots in wood, protruding nailheads, etc. At the end he talks about how to put all these methods together into a complete composition, and gives tips on working from photographs. I have not yet tried all of Hillberry's techniques, but the ones I have used have helped me immensely. I would highly recommend this book to any intermediate to advanced level artist.