A deep dive into set theory and basic topological notions.
The search for is understandable—every student wants free, instant access. However, Paul E. Long’s masterful little book is easily worth the cost of a pizza . The Dover edition is ethically priced, legally purchased as a PDF, and will serve as a lifelong reference for continuous functions, compactness, and connectedness. an introduction to general topology paul e long pdf link
In a crowded field of topology textbooks, Long’s work stands out for three reasons: A deep dive into set theory and basic topological notions