An introduction to functional analysis for science and engineering

Seem reasonably concise, but I think Kreyzsig's Introduction to Functional Analysis with Applications fills the "gap" that this paper wants to fill. It's readable, has applications, exercises, and is more complete.

That sure is one compact document. Pun intended. The document is very readable too.

(2019). No exercises.

Genuine question: does the writing tool matter at all here if the exposition is clear and mathematically correct? I’ve seen great notes written in Word, LaTeX, and even slides—quality seems independent of format.

Not LaTeX...