House of Doors Series by Brian Lumley

Bent on taking over the Earth, the deadly Thone have planted a monstrous device on our planet's surface. Trapped inside is a group of scientists, spies, and innocent bystanders. Part maze, part torture chamber, part laboratory, the House of Doors is a test. If its captives survive, the Thone will withdraw from Earth and leave us in peace. Survival seems impossible. At every turn of the labyrinth the prisoners encounter alien world and terrifying monsters ripped from their own subconscious fears... moreBent on taking over the Earth, the deadly Thone have planted a monstrous device on our planet's surface. Trapped inside is a group of scientists, spies, and innocent bystanders. Part maze, part torture chamber, part laboratory, the House of Doors is a test. If its captives survive, the Thone will withdraw from Earth and leave us in peace. Survival seems impossible. At every turn of the labyrinth the prisoners encounter alien world and terrifying monsters ripped from their own subconscious fears. Only by defeating the demons within can these men and women escape the House of Doors and save the Earth. less

Alien beings bent on our destruction have seeded the world with horrible machines capable of transforming our planet into a hellhole where only they can live.Our only hope is to solve the puzzle of a four-dimensional maze, an alien thing that is part building, part machine, and part psychological torture chamber. A few brave men and women--and one fearless dog--dare to enter the maze... moreAlien beings bent on our destruction have seeded the world with horrible machines capable of transforming our planet into a hellhole where only they can live.Our only hope is to solve the puzzle of a four-dimensional maze, an alien thing that is part building, part machine, and part psychological torture chamber. A few brave men and women--and one fearless dog--dare to enter the maze. What they find there will change their lives forever, as the alien machinery creates terrifying worlds based on their worst nightmares. less