The Rage of Cthulhu by Gary Fry
When George Cox chances upon a disused foghorn station on the English coast, he wonders what could have been big enough to cause so much damage to it. His investigations take him and his wife all around the world, tracking down stories about an ancient creature rumoured to have occupied the planet hundreds of thousands of years ago. Even if such a creature existed, it had to be dead now, hadn't it? At any rate, it couldn't be haunting George's dreams. It couldn't be summoning him from its immense grave. But the closer George comes to the truth, the more he learns that all the travel guides lack one vital piece of information: In his house at R'lyeh dead Cthulhu waits dreaming.