I figured you must be familiar with it. It was the first treasure-hunting book, wasn't it? Or at least the first modern attempt, especially with a treasure that valuable? I bought it when it came out, and it is still interleaved with bits of scrap paper on which I scrawled my pathetic attempts to solve the riddles.
Ha, Life: A User's Manual is an influence, too! I was working at Godine when a copy of the French original showed up, and it was my responsibility to find a reader for it. It got a very positive review, I recall, but it wasn't until long after I left the company that David finally got around to publishing the translation. I always regretted that I wasn't there to shepherd it to publication.