If I had to recommend just one candy book to everyone, it would be Peter Greweling's Chocolates and Confections at Home with The Culinary Institute of America. (Yes, I would recommend this over my own book!) Greweling's book is just so comprehensive, and really delves into the how's and why's of candy-making. He provides in-depth scientific background for many important candy concepts, as well as hundreds of step-by-step pictures of various techniques. If you really want to understand the fundamentals behind many candy techniques, this is the book for you!