Robert Ghrist offers his Elementary Applied Topology for free on his site. It's useful more as a supplement or survey than a primary text to learn. https://www

Robert Ghrist offers his Elementary Applied Topology for free on his site. It's useful more as a supplement or survey than a primary text to learn. https://www.math.upenn.edu/~ghrist/notes.html https://www.math.upenn.edu/~ghrist/notes.html