Basilisk

A terrifying and unputdownable horror-thriller novel of fiendish puzzles, compelling mysteries and paranoia about an enigmatic hacker, a deadly online game, and a cyber weapon that makes people go insane. Perfect for readers of Paul Tremblay, Neal Stephenson and Mark Z Danielewski's House of Leaves, and the people who just have to know the answer.
Alex Webster is an ethical hacker who, like most hackers, prefers questions to answers. So when she and a colleague, Jay Morton, stumble across a mysterious game created by a shadowy figure known as The Helmsman, they are instantly hooked.
As they solve increasingly bizarre puzzles and uncover The Helmsman's deranged manifesto, they are pursued by a sinister group known only as XXX XXXXXXX XXXXXX, who will do anything to stop them uncovering the Basilisk, a cognitive weapon which makes anyone who understands it lose their mind.
When Jay disappears, as they hone in on the truth of the Basilisk, Alex is left trying to piece together what's happened to her friend, escape the awful smiling glitch people stalking her every move, and solve The Helmsman's final puzzle.