The unique thing about Fit for Developing Software is the way it addresses the interface between customers/testers/analysts and programmers. All will find something in the book about how others wish to be effectively communicated with. A Fit book for programmers wouldn't make sense because the goal is to create a language for business-oriented team members. A Fit book just for businesspeople wouldn't make sense because the programmers have to be involved in creating that language. The result is a book that should appeal to a wide range of people whose shared goal is improving team communications.