The only thing I knew about this movie going in was the infamous scene where Max von Sydow plays chess with Death. Full disclosure: I knew of the scene in Bill and Ted's Bogus Journey where the eponymous duo play, among other things, Twister with Death. Been awhile since you watched that 90s classic? Take a look at the clip. It's worth the full four minutes.
I guess the existence of this reference alone makes The Seventh Seal book-worthy, but there's also the many best-of lists on which it appears. And the whole Bergman thing.