Knuth&#x27;s <i>Art of Computer Programming</i>. Seriously. On the one hand, it will teach a lot and require stretching. On the other hand, there will be much of the mathematics that is simply beyond ability so there are a lifetime&#x27;s of challenges.<p>Placing it all in the context of computer science may make it more fun if that&#x27;s your interest. Volumes I and IVa in particular.