What books would you recommend on Mayan spirituality?
I recommend my own, just because it was an odyssey to write it and it was meant as a thorough and heartfelt guide for beginners. And I would recommend The Mayan Factor, by Jose Arguelles.
I know there are a lot of other titles out there, and I believe that anyone who writes a book has a mastery that is hard to match. But I am committed to Natural Time, much more specifically than to Mayan spirituality in general, and there is not a lot out there to be found on that strain of Mayan mysticism.
And ultimately, I would say no book will teach you what the Tzolkin itself can demonstrate through experiencing its cycles.