Diablo IV is one of the most poorly-kept secrets in the videogame industry – it’s one of Blizzard’s biggest franchises, and the developer has all but confirmed that a new non-mobile game is on the way –  and that trend continues today, as a new magazine ad for a Diablo book seems to have leaked a pending announcement of the sequel. The latest issue of German magazine GameStar (spotted by VideoGamesChronicle) contains an advertisement for the upcoming book The Art of Diablo, by Jake Gerli and Robert Brooks. It’s an official book published by Blizzard itself, and will be available around November 21. The ad for the book says that it features “over 500 artworks” from Diablo, Diablo II, Diablo III… and Diablo IV. This is no typo – it’s a real magazine ad about an official Blizzard product – nor is it a mistranslation, as despite being in German it clearly lists “Diablo IV” amongst the games being covered in the upcoming art book.