Jane Grigson's Charcuterie and French Pork Cookery is my favourite. It's very well written and really inspirational but focuses only on curing from the one area and the lack of photos put off beginners. Charcuterie: The craft of salting, smoking and curing by Brian Polcyn and Michael Ruhlman has great photos and recipes from more countries but doesn't have quite the depth of French Pork Cookery
I have used, and would recommend, Charcuterie:The Craft of Salting, Smoking and Curing. The book is written by Michael Ruhlman and Brian Polcyn. It is well written, straightforward and educational. The authors are also typically available for advice if you need it.
I also own this book and would recommend it.
"The Art of Charcuterie" by John Kowalski, published by Wiley. If nothing else Wiley publishes authoritative books on some of the more arcane aspects of culinary arts and sciences.
I have to concur with the others that "Charcuterie: The Craft of Salting, Smoking and Curing" by Michael Ruhlman and Brian Polcyn is a great resource. This is a fun book to work through, is clearly written and well organized for the home cook.
For more detailed explanations on meat science and a broader set of recipes, I recommend "Home Production of Quality Meats and Sausages" by Stanley and Adam Marianski. This is laid out more as a reference book and has very in-depth information, but in my opinion is a good secondary resource once you get into the hobby and are looking for graduating to the next level.
Another vote for Ruhlman's Charcuterie book. I've made recipes from it and they've turned out fantastically, but it's also wonderful to just sit around and read.
Charcuterie: The Craft of Salting, Smoking and Curing