Daffodil by Noël Kingsbury is a gardening reference to the history and breeds of daffodil. Along with the practical information are numerous, luscious photographs by nature photographer, Jo Whitworth.
One of the most interesting discussions early on in Daffodil is on division between narcissus and daffodil. Here in the States, it seems that anything that isn't the classic daffodil shape and color ends up being sold as a narcissus. According to Kinsbury, there really isn't a difference between the two and she calls all of the followers, regardless of shape, size or color, daffodils. I like this approach (for a hobbyist gardener, I'm terrible at remembering flower names).
Later sections of the book are divided into the different types of daffodil by their shape — number of pedals, trumpet length and shape, and colors. Having only grown a couple varieties myself, I had no idea there was as much variety as there is.
As this book is gorgeous to look at, it would also make a great coffee table book. It's a useful reference and one to put out when guests come by.