We've seen our share of bizarre, baffling works of art and fiction that were totally intended to scare their readers, but it's another thing to encounter a supposedly “serious” publication that looks like its author once visited a nightmarish alternate universe... and was driven mad by it.
The sanity of Italian artist Luigi Serafini is not in question, as he's currently alive and well. But you can't deny his famous book Codex Seraphinianus reads like the work of a man driven to insanity by what he saw on the other side – like the character Abdul Alhazred, fictional author of the Necronomicon referenced in many of H.P. Lovecraft's classic tales like At the Mountains of Madness. In fact, some of the creatures depicted in the Codex resemble Guillermo del Toro's concept artwork for his long-delayed film adaptation of Lovecraft's story.
Like the Necronomicon, this eleven-chapter book features a vast quantity of eerie text in an unknown language (linguists are still unable to decipher it; Serafini himself says it's meaningless), alongside detailed illustrations featuring everything from mutated animals and sentient plants to biomechanical humans and horrific monsters... as well as bizarre rituals that seem to combine all of the above.
Unlike Lovecraft's fictional tome, the Codex is very real: it was first published in 1981 and you might still be able to get your hands on a copy... just be prepared to pay a hill of cash for it. Copies of the first edition have sold for over $5,000, and even the 2013 printing usually can't be found for less than $80.