well, im only on the first book, and its a 4 book seriese.
but so far at least, its about Roland "the gunslinger" chasing a un-named "man in black" Roland wants the man in black for some reason, but it hasnt really said why, throughout his journey through this barren wasteland (its a desert, where nothing can grow, save 'devil grass' a hallucinogenic producing grass, that also causes rapid mutations) with mutant animals, and people so desperate for water, he was begged (literally) to piss in a cornfield just so the plants can grow. the world seems to have regressed to ways similar to that of the old west.
its really bizarre, a little hard to understand at a few parts, but i like it.