If you're interested in the 'cracks' with regards to NDEs, definitely read The Spirit Molecule by Rick Strassman. That book, along with a few Terence McKenna lectures, will destroy any last vestiges of a materialistic worldview.
(To learn more about Terence McKenna, start with these:
It's always healthy to be versed with the opposing viewpoint, so I'd suggest reading How the Mind Works by Steven Pinker for a well articulated and evidenced materialistic thesis.
(To learn more about Terence McKenna, start with these:
http://www.matrixmasters.net/salon/?p=254 (also part 2 and 3)
http://www.matrixmasters.net/blogs/?p=297)