As other reviews have mentioned, Birmingham IV was originally written using the text adventure design system Quill in the late 1980s but then ported to Inform 7 in 2014-16. The current version still retains the feel of a non-Infocom text adventure circa 1989. By way of comparison with some other old-school games in IFComp 2018, Birmingham IV feels more modern than Flowers of Mysteria or Escape from Dinosaur Island but less modern than Bullhockey!.
The setting appears to be the area around Birmingham (England) in the early to mid-1600s: Queen Elizabeth’s face appears on some money you find, and there’s a reference to the Virginia colonies. It’s not clear what the plot is, though. You play as the Phil, a scholar and scientist. Or, as they would say back then, “natural philosopher.” In fact, as you eventually come to realize, “the Phil” is actually a title - “the Philosopher” - not the name of the PC. You can explore your cottage and the surrounding area, and there’s a note from the parson that gives you a couple of long-term goals, but for the most part at the beginning of the game you just wander around solving puzzles. As you keep playing, though, the end-goal eventually becomes clear. Or "end-goals," I should say, since Birmingham IV gives you a choice at the end.
There's also magic in this world. But it's a subtle magic - magic of an old English kind, where elves are tiny and fearful of humans and where ancient skulls and standing stones are infused with power that you can use but never really understand. In terms of how magic is portrayed, there's a pretty clear line running from English folk tales to The Lord of the Rings to early Dungeons & Dragons to the current canonical takes on fantasy races in role-playing games (both computer and paper), as well as many modern works' systematic and almost scientific approach to magic. Even Infocom's Enchanter series takes this systematic approach, and the Harry Potter series does as well. In the latter, magic is something almost mundane: It has been apportioned into school subjects to be learned as a matter of course by children! Birmingham IV, however, is solidly pre-Tolkien: Magic is mysterious, ethereal, and perilous. For me, that was refreshing, and Birmingham IV's consistent take on this constituted much of the game's charm.
Unfortunately, Birmingham IV has some weaknesses, playability-wise, that affected my enjoyment of the game and that will frustrate many modern players. (1) The game does not always tell you which directions you can travel in. It doesn’t take much additional effort on top of drawing a map (if you’re doing that) to figure out which directions are allowed, but it will be a hurdle for modern players. (2) There are a few too many one-way directions near the beginning of the game. (3) You have an inventory limit of five. (4) It is easy to get yourself into an unwinnable state without realizing it. (5) Many of the puzzles are underclued. The puzzles I'm thinking of for which this is the case aren't bad puzzles, but some of their solutions are the kinds of things that you wouldn't come across unless you had the patience to try a bunch of random things that might work. (Fortunately, David Welbourn has published an excellent walkthrough!)
In other words, Birmingham IV is a huge, old-school piece of late 80s IF. If you enjoy that sort of game, then you'll probably enjoy Birmingham IV.