Textbook: Nguyen Phu Hy, Functional Analysis, Science and Technics Publishing House, Hanoi, 2005 (in Vietnamese). Bai-tap-Giai-tich-ham
Further reading: Joseph Muscat, Functional Analysis - An Introduction to Metric Spaces, Hilbert Spaces, and Banach Algebras, Springer, 2014.
Sample test [pdf]