A good book of functional analysis
I am an algebraist and not an analyst, however my favourite book on this area is "Walter Rudin: Functional Analysis".
I am not an analyst of any sort, so you do not need to listen to me, but I really like Lax's "Functional Analysis".
Some of the good books are:
Elements of the Theory of Functions and Functional Analysis by Kolmogorov, Fomin.
Functional Analysis, by F.Riesz and Nagy.
Functional Analysis : Spectral Theory by V.Sunder. Freely available here.
Analysis now. By Gert Kjeargård Pedersen. (As suggested by Theo Buehler at $\textbf{Math.SE}$
Stein, Elias; Shakarchi, R. (2011). Functional Analysis: An Introduction to Further Topics in Analysis. Princeton University Press. ISBN 0691113874.
Functional Analysis, Sobolev Spaces and Partial Differential Equations (Universitext) by Haim Brezis.
Elementary Functional Analysis by Georgi E. Shilov.
Introductory Functional Analysis with Applications by Erwin Kreyszig.
Notes on Functional Analysis by Rajendra Bhatia. (Hindustan Book Agency.)
Functional Analysis by S.Kesavan. ( Hindustan Book Agency.)
Elementary functional analysis By Barbara D. MacCluer
Functional analysis: an introduction By Yuli Eidelman, Vitali D. Milman, Antonis Tsolomitis (AMS)
Principles of functional analysis By Martin Schechter. (AMS)
You may also want to see this thread: Problem books in Functional Analysis
$\textbf{Note.}$ The books which are written in Italics are the ones which I have read partially. The ones which are not in Italics are the ones which I have come to know (by friends, teachers) are good books in Functional Analysis. Also, I really don't know which publisher actually publishes the book in foreign edition written by Kesavan and Bhatia.