
This is an introduction to the basic tools of mathematics needed to understand the relation between knot theory and quantum gravity. The book begins with a rapid course on manifolds and differential forms, emphasizing how these provide a proper language for formulating Maxwell's equations on arbitrary spacetimes. The authors then introduce vector bundles, connections and curvature in order to generalize Maxwell theory to the Yang-Mills equations. The relation of gauge theory to the newly discovered knot invariants such as the Jones polynomial is sketched. Riemannian geometry is then introduced in order to describe Einstein's equations of general relativity and show how an attempt to quantize gravity leads to interesting applications of knot theory.
But I've enjoyed the following texts to a larger extent than others:
- Algebra: Chapter 0 (Aluffi)
- Real Mathematical Analysis (Pugh)
- Mathematics and its History (Stillwell)
- An Introduction to Manifolds (Tu)
- Gauge Fields, Knots and Gravity (Baez)
- A First Look at Rigorous Probability Theory (Rosenthal)
- All of Statistics (Wasserman)
There are some authors I trust and am happy to buy so long as the topic vaguely interests me: VI Arnold, Tristan Needham and John Stillwell.
I really like the list put out by @enriquto in a separate comment, but I've avoided duplicating those recommendations in the list above.
If you have a background in physics then some combination of Nakahara's 'Geometry, Topology and Physics' and Baez and Muniain's 'Gauge Fields, Knots and Gravity' might be good (I haven't included relativity textbooks as I assume it you have a background in GR then you have enough differential geometry).
An unusual recommendation that I think is really nice is 'Stochastic Models, Information Theory and Lie Groups' by Chirikjian. It covers a few other topics mentioned in this thread and is really nice. It's _extremely_ concrete and spells out a lot of calculations in great detail. Plus, the connection to engineering applications is much more obvious.
[1]: http://www.worldscientific.com/worldscibooks/10.1142/2324