I already have the books in hardcover – all hail the mighty Kickstarter – but Hillfolk is one of those game systems that can be valuable to a GM even if you don’t actually play it, so by all means: grab it from Bundle of Holding. Robin Laws consistently comes up with gaming innovations that are both interesting, and entertaining to play. …This is not all that common, alas.
And he’s right: it’s being offered an absurdly low price.
Moe Lane
PS: The Bundle of Lamentations (Lamentations of the Flame Princess, to be precise), on the other hand, is something I know nothing of.