Dan's Inferno

Robert Blandon is the world's greatest puzzleologist. Crosswords, Rubik's Cubes, Sudokus - he can do them all. When he flies to Florence to visit a renowned professor, Blandon finds himself drawn into a mysterious web of underground tunnels, secret societies and really hard anagrams.

Extensively researched by looking at Wikipedia and talking to a man in a bar about conspiracy theories, <...