This book explains why a motorcycle does what it does, and the proper calculations and physics for what we feel when we ride.
It isn't a recreational read, and doesn't have big glossy pictures of MotoGP riders, but it is big on real facts. And if you understand 10% of this then you will be a better rider for it. For an example look at material on centre of gravity - I'm still getting my head around it, but the little I do understand so far explains why the stuff I learned motocrossing actually works.