There are a huge number of books out there on this subject and many great authors. The following is a very small selection of books I have read or have had recommended to me.
Mayan Studies, Calendar, 2012, Galactic Alignment etc
The Mayan Factor - Path Beyond Technology - Jose Arguelles
Though I don't agree with the dreamspell calendar and the shifting of the Tzolkin in relation to the Gregorian Calendar, this is a great book, if a little hard to access that gets you thinking about humanity and the Earth in a galactic context.
Maya Cosmogenesis 2012 - John Major Jenkins
This is an easy to read book that demonstrates the solid research from which John explains that the 21 December 2012 is a key point in the Earth's evolution where the winter solstice sun is aligned with the galactic centre and cool things will happen.
The Mayan Calendar and the Transformation of Consciousness - Carl Calleman
Another good book that outlines the Nine Underworlds and how they contribute to the transformation of consciousness.
