Undergraduate math books with a "plot"

Question

I usually have trouble trying to read huge tomes without any proper motivation - there's no feeling that I'm "working" towards something. Perhaps I've been spoiled by "Abel's Theorem through Problems and Solutions" by V.B Alekseev which builds up group theory solely to prove the insolubility of the quintic, but it was nice knowing there was something "big" at the end of it all. I'm looking for books in a similar vein, that might focus on a single question and build a story around it.