I will be taking Functional Analysis next semester and am looking for an appropriate book. I have taken Algebra (Aluffi "Algebra: Chapter 0"), Measure Theory (Elstrodt "Maß- und Integrationstheorie"), and Exterior Analysis (Tu "Introduction to Manifolds"; Wedhorn "Sheaves, Manifolds, and Cohomology"). Complex Analysis will be given next semester.
A book like Helemskii is almost perfect, however since exterior analysis is not a prerequisite, manifolds are not used. So Ideally I'm looking for a book.which uses manifolds and hopefully (but not necessarly) category theory.