I: Functional Analysis: Volume 1: vol 1 (Methods of Modern Mathematical Physics) (Methods of Modern Mathematical Physics, Volume 1) Hardcover – 23 Feb. 1981

This book is fantastic. It is beautifully written. The authors motivate all of the theory, making it seem as natural as possible. This aspect seems to be missing from all the other standard Functional Analysis texts I have read. I feel the authors really want to share the ideas with me. All too often authors and teachers seem to prevent you from understanding, perhaps because they are not willing to do the hard work of explaining clearly, or perhaps because they want to make themselves seem more intelligent than you. In fact, Reed's and Simon's generous, painstaking, welcoming approach means that they are brighter by far than their competitors ! I borrowed this book from the library a few days ago, since when I haven't put it down ! I knew straight away that I needed to buy my own copy.

Works fine.