There is a fair consensus amongst those who come to consensuses about such matters that Tolkien wrote The Lord of the Rings primarily as a way of exploring Middle Earth - that is, this is what is known as a milieu story, in which the setting, the world, drive much of the plot. In The Two Towers this is on fine display again. One of the more interesting things to do with a copy of The Lord of the Rings is to sit down and look at just how much ground is covered by the various journeys; you then realize just how large a world Middle Earth is, and how small a section is explored in these tales. The distance covered by Frodo and Sam through such great peril and difficulty in the entirety of their chapters in The Two Towers is essentially a tiny corner on the map.
As I said in my review of The Hobbit, during this reread I was surprised by how light that novel is; I suspect that my memory of its tone from my last reading was affected by my intermediate viewing of the movies. Or, perhaps I was merely linking it with the core Lord of the Rings books, which very quickly take on a markedly different tone from their prequel (and yes, I know that technically there is just one "book," which was split into three parts for the convenience of readers and publishers). The implications of a darker turn are heavy throughout even the early chapters of The Fellowship of the Ring, but are pivotally confirmed with the events of the chapter A Knife in the Dark.
One of the distinguishing features of the speculative fiction genre in its published form is the maps. Avid readers of fantasy and science fiction are known to pour over the maps included in the books they read, maps describing fantastical worlds and universes in vivid detail. It was perhaps inevitable, therefore, that I would at some point be obliged to create maps to go along with the stories I've written or am in the process of writing.