Probably not a perfect book for someone at the HS level, but just a bit past that I would HIGHLY recommend MacLane’s Mathematics Form and Function. It’s a revi

Probably not a perfect book for someone at the HS level, but just a bit past that I would HIGHLY recommend MacLane’s Mathematics Form and Function. It’s a revisionist history of mathematics aimed to demonstrate how ideas flow from one to another. He eliminates a lot of dead-ends and takes a perspective as to one “ought” to move from one subject or discovery to another. OTOH, the historical perspective is both readable and often a missing piece which makes other math tougher.