We had a great question about the 5e version of Borderlands on another thread, about the general flavor of the campaign and the basic approach to this book specifically, from someone who hasn't previously gotten any of the Frog God Games products. Here's from the answer I gave:
First, the campaign book is designed for traveling adventurers, the type that prefer hitting the road and picking their own destinations rather than following a set adventure path or exploring hex-by-hex. The Firefly series and the Traveller game are good analogies in science fiction. So it's at its strongest for a DM who likes making up his own adventures or using modules, as opposed to longer pre-programmed series. (for non-5e DMs, those big series are already located in the area, but unless you enjoy converting stuff they aren't relevant to you as a 5e player). The campaign area absolutely doesn't depend upon you having any familiarity with those resources, incidentally -- it's absolutely stand-alone. It's designed around travel, like I said, with a scattering of multiple one-session lairs throughout, and the adventure book provides seven longer adventures - again, not a series.
In terms of the flavor of the place, if you're familiar with Clark Ashton Smith's Averoigne stories, those are the best analogy. There's also a lot of influence from Jack Vance (more on the Lyonesse side than the Dying Earth side). Both of those authors portrayed worlds with a veneer of civilization under which there are some horrific realities lurking, both supernatural horrors and also horrors of human nature. Borderland Provinces weaves in and out the description of the veneer (government, trade, culture) and of the underlying menaces and horrors (the descriptions of monster lairs, ongoing villainous plots, and other such DM information).
