How best to read postmodern texts?
First, more than most literature, postmodern literature needs multiple readings. At any minute you might be thrust backward into the early 19th century, and it's going to take a while to figure that out. The author is often trying very hard to disorient you-so be patient and flip back a few pages early and often.
Second, sometimes you just have to go with it. If you're following a story about a fever epidemic in the 19th century and then a contemporary voice comes along describing the Philadelphia fire, make a note in the margin ("who the heck is speaking now?") and keep going. Postmodern texts often rely on sharp juxtaposition of voices and historical periods, so trust that it'll make more sense on re-reading and keep plowing ahead.
Postmodern literature can present some of the most difficult reading out there, but it also offers some of the best intellectual challenges.