Hello, good people of /wsr/. I am looking for a recommendation for a good introductory book on sets and set theory, something with proofs as well. My issue is that books involving proofs oftentimes skip steps when laying out the proof, assuming instead that you know how the jump from one step to the next came about. At least, that's how it feels to me. I want something that instead is relatively easy to understand for a beginner, but one that is also clear enough in its proofs. For context, I'm interested in modal logic. To be able to understand a lot of what goes on there, foundational knowledge in set theory seems necessary. I tried going through An Introduction to Classical and Modal Logics by Adam Bjorndahl and I became stuck very quickly since even the set theory that's explained in that book is done in a way that is a bit above my level, or is at least not as simplistic in its layout of proofs. I would appreciate any assistance in finding a book that works for me.