In advance of next week's bookstore release for Isis, horror author Douglas Clegg's latest novel from his Harrow haunted mansion saga, Vanguard Press and put out promotional Flash game that has so far attracted more than 1.4 million plays from 1.3 million unique players.

Distributed through "major arcade portals and hundreds of other smaller gaming sites", the simple spot-the-difference game highlights colorized versions of the book's pen-and-ink illustrations from Glen Chadbourne, who also recently contributed artwork to Stephen King's graphic short story The Secretary of Dreams.

The game's success caught completely by surprise -- the company expected it to attract a million plays in the first two months, not after just ten days since it was posted online. The release is also doing its job of generating interest for the book, directing some 10 percent of players to Isis's site.

In fact, publisher Vanguard it so pleased with the game, it plans to put out an iPhone/iPod Touch-specific version this fall with the hope of attracting both more players and more Isis readers. This really is a multimedia production! There's even an Isis trailer -- it's not very informative, and you might want to turn down your volume for it, but it shows off some of Chadbourne's art:

"I’m excited to be part of a very different kind of book promotion that hasn't been done in quite this way before -- where the outreach is viral within the game community itself and has a life beyond the usual time period for getting word out about a book," says Isis's author David Clegg.

You can play the game and read an excerpt for the book at Isis's official site.