Emily Yellin's Your Call is (Not That) Important To Us is a fast, fun read about the customer service/call center business, with a little bit of IVR thrown in. The book does well when it describes the history of customer service. There are some insights into companies that try very hard to get it right, like FedEx and Zappos and Jet Blue. It doesn't do as well with the speech IVR material. She grants too much credibility to fringe players like the MIT profs who want to create "emotional" computers and the companies pushing interactive avatars.
One of the central observations in the book is that customer service doesn't occupy a very high place in the list of priorities at most companies. This I've seen many times in the companies I've worked for or consulted with. Personally, I'd love to work at a company that decides at the highest levels that customer service is a top priority. The challenges of getting customer service right are very hard, even with a lot of support from executives. Without that support, it's impossible.