'… this is unquestionably a valuable book, written at an accessible level for graduate students while providing a nice summary of the last century's - and notably the last two decades' - developments of these methods. I do not doubt that this will be a popular book; it fills a hole in the textbook/monograph literature that's needed filling for at least ten years. Moreover, the author's style is relaxed and crystal clear while maintaining mathematical precision and power.' Charles Doering, University of Michigan