These books really challenge your thinking or force you to think hard and/or see things through another lens. They are also really good reads that are very hard to put down.

Harry Potter and the Methods of Rationality Firefall series by Peter Watts (Blindsight & Echopraxia) Axiomatic by Greg Egan N.N. Taleb's books

These are all books I had seen written about in previous HN threads like this and ended up reading, so glad I did!