BTW, counterexamples in mathematics are really important and often help to refine definitions and sharpen proofs.

1) I recommend the wonderful 1976 book Proofs and Refutations by Imre Lakatos.

2) There is a considerable list of books dedicated to counterexamples, e.g. in topology, probability, analysis, etc.

[1] https://en.wikipedia.org/wiki/Proofs_and_Refutations

[2] https://www.amazon.com/s?k=counterexamples