Someone above linked a writing he had about pomo that I almost completely agree with, the main problem with it being that understanding it pre-rationally leads to nihilism. That does not, however, mean that pomo is nihilistic, only that incomplete interpretations of it are.
Postmodernism as a canon is almost too powerful for its own good, which is ironic in that each of the individual writers almost aspire to powerlessness in their desire to eliminate modernist structures of domination. There have been a few times in my life where I could literally feel my perspective on the world shifting to a higher mode in an instant, the first was with Sartre, and the most recent was with Foucault. Approaching it at the right time and with the right teachers can fucking change your world, but the process to get there is heavily individualized and I fear perhaps can't be standardized. If you don't arrive willing to accept the ideas as divers furtherances on your own conceptualizations, you will reject it as nihilism.