If you're more interested in the science side, you might like James Austin's Zen and the Brain. It's a bit old, but pretty interesting. For more modern analysis of meditation, the Mind and Life Institute has funded a lot of research, but much of it requires access through a university library, sadly. (Google Scholar might help.)

Also, if you're open to the idea that there might be more, but like me, not interested in anything mystical, I highly recommend checking out Stephen Batchelor's Buddhism Without Beliefs.