If you are looking for a digital version that is safe and high-quality, try these routes:
It strips away the dense prose found in traditional textbooks (like Rudin or Kreyszig) and gives you the definitions and theorems you need to solve problems. schaum functional analysis pdf patched
You can often "borrow" a digital copy of Schaum’s Outlines for free. This is a legal, scanned version of the physical book. If you are looking for a digital version
Provides lecture notes and assignments that mirror the content found in the Schaum’s outline. schaum functional analysis pdf patched