I got this together with Charcuterie, by the same authors. This review will cover both books.
Charcuterie covers sausagemaking while Salumi is about dry curing whole cuts of meat. Both books focus heavily on the Italian styles.
The books contain a great deal of information regarding their topic (the word charcuterie encompasses sausages, cured meats and other foods such as pates and terrines). Unfortunately, some of this information is incomplete, misleading or simply wrong. For a full discussion of errors, search the usual food-related forums.
The books themselves are very nice, with beautiful photographs. In my opinion, this betrays the principal weakness in the books: They can't decide if they're cookbooks or coffee table food porn. The text reflects this, with little essays and anecdotes about the authors' childhoods, travels etc. interspersed with the recipes and techniques. This is per the standard of foodie books, but frustrating for the reader who wishes the authors covered more ground and properly tested and proofread their recipes.
On the plus side, the books are informative (when they're correct...) and the many line drawings and diagrams included are useful for learning Italian-style pork butchering.
If you're interested in making Italian-style cured meats and can tolerate the silly filler, these are probably the books to read. Just remember to check online for corrections...