Bletchley Park: famed home of the Enigma machine, Colossus computer, and, according to the premise of TR-49, an altogether stranger piece of tech. According to the tantalising lore of this mystery game, two engineers created a machine that feeds on the most esoteric books: treatises on quantum computing, meditations on dark matter, pulp sci-fi novels and more. In the mid-2010s, when the game is set, Britain finds itself again engulfed by war, this time with itself. The arcane tool may hold the key to victory.

You play as budding codebreaker Abbi, a straight-talking northerner who is sifting through the machine now moved to a crypt beneath Manchester Cathedral. She has no idea how it works and neither do you. So you start tinkering. You input a four-digit code – two letters followed by two numbers. What do these correspond to? The initials of people and the year of a particular book’s publication. Input a code correctly and you are whisked away to the corresponding page, as if using a particularly speedy microfiche reader. These pages – say, by famed fictional physicist, Joshua Silverton – are filled with clues and, should you get lucky, further codes and even the titles of particular works. Your primary goal is to match codes with the corresponding book title in a bid to find the most crucial text of all, Endpeace, the key to understanding the erudite ghosts of this machine.

Hidden within this rhizomatic network of information is a mystery so intriguing and elegant that it can unfold naturally from any individual player’s investigations – no matter which titles or authors you see first, or where your particular curiosities lead you thereafter. Connections can cascade, tumbling like a waterfall, before swerving in unexpected directions, defying the traditionally linear logic of mystery fiction. TR-49 gives you an in-game notepad to keep track of everything; I recommend also keeping an actual pen and paper beside you.

Paper trail … TR-49. Photograph: inkle Ltd

You might imagine TR-49 as a comment on the rise of AI large language models (LLMs) which “scrape” data as this game’s machine feeds on writing. Actually, its concerns are broader and more ambitious, recalling the heady recent books of Chilean author Benjamín Labatut (When We Cease to Understand the World and The Maniac). Like Labatut, TR-49 brims with awe, scepticism and horror at the reality-shredding possibilities of scientific and technological advances made in the 20th century, all while pushing these concepts into a playful, fantastical space.

Less compelling are conversations that play out between Abbi and her companions on the other end of a radio transmission. Where the mystery told through the machine itself is lavishly detailed, what happens outside it feels too thin: Abbi’s reasons for being there; the nature of the conflict raging above, which is sketched in frustratingly vague terms.

Still, the interactive heart of TR-49 resides in trawling this codebreaking device for secrets. And in this regard, the game is an unqualified success; TR-49’s database mystery rivals Sam Barlow’s games Her Story and Immortality, though it is of an unashamedly literary nature compared to those more filmic works.

Closer to TR-49’s beginning, you may feel crushed by this mass of inscrutable writings. Quickly, you will swim elegantly amid it, conversant in its many, many peculiarities. Across a handful of evenings, I relished disappearing into this archive, cavorting from log to log, title to title, following threads and losing track of time. Each scrap of paper, water-damaged periodical and rare first edition threatened to solve this mystery, yet none could in isolation. Just as the fictional maker of the archive fell under the spell of these records and materials, I too was seduced.