This is a delightful and useful book. At least three kinds of people should buy it:
(1) People in computational linguistics and natural language processing. If you work in speech recognition, you need homophones to test (or illustrate challenges for) speech recognition systems. If you work in natural language processing, you need homographs to test your system's ability to handle lexical ambiguity. This book is a great source for both.
(2) People in phonetics and sociolinguistics. If you do experimental work in these fields, you want lots of minimal pairs. Although they're not labelled as such, this book will point you towards lots of minimal pairs for flapping, glide raising, and other phonological phenomena of English.
(3) People interested in the English language in general. I came across lots of interesting and cool words in here, and enjoy just flipping through this book.
In addition, the book is beautifully printed and bound. I would have expected it to cost a lot more.