In 1995 or 1996, British musician Cylob — real name Chris Jeffs — picked up a free booklet from a stack near the entrance of a London bookshop. A staffer said someone mysterious kept leaving them there.
The booklet has 20 pages, no letters, no numbers, not even page numbers — just rectangular symbols arranged in grids across the pages. No other copies are known to exist.
Crypto blogger Klaus Schmeh wrote it up in 2015 after a reader tipped him off, and cataloged it at #00056 in his encrypted books list. A reader named Torsten built a transcription table and counted 24 distinct symbols — the right number for a simple English substitution cipher. But roughly half of them appear only in the first section of the booklet, with near-identical variants taking over in the second half. That pairing might bring the actual symbol count below what you'd need to encode 26 letters.
The leading theories as to the meaning: a substitution cipher (though the math symbols don't quite work out), a game accessory (the professional printing suggests multiple participants, and the diagrams on most pages could represent levels or platforms), or art without any hidden meaning at all.
Schmeh brought it to Elonka Dunin, who wrote Codebreaking: A Practical Guide with him, and she noted that escape rooms and geocaching didn't exist in 1995 — so whatever organized challenge this might have been part of predates those formats by a decade. Or it's an elaborate joke. Nobody has come forward either way, according to Schmeh's blog.
Previously:
