There's a Richard Matheson omnibus up for sale at Amazon. Two books I've heard of, two I haven't.
The reviews on the Amazon page are actually for the Matheson collection Nightmare at 20,000 Feet, FYI.
Richard Matheson Suspense Novels: The Shrinking Man, Camp Pleasant, Hunger and Thirst, 7 Steps to Midnight - $3.99
The Shrinking Man: While on vacation, Scott Carey is exposed to a cloud of radioactive gas—and begins to shrink at a fraction of an inch per day. As he loses his stature, his relationships with his spouse, family, and friends are also threatened—as is his life. The inspiration for several movies, this novel raises interesting questions about the meaning of masculinity in 1950’s American suburbia.
Camp Pleasant: As a first-time camp counselor at a boy’s summer camp, Matt Harper is the witness to a murder. Told with jarring simplicity, this novel tells the story of casual brutality in an environment that should be representative of idyllic childhood innocence.
Hunger and Thirst: In renowned science fiction and horror writer Richard Matheson’s first novel, the protagonist lies paralyzed in a hospital bed after catching a bullet in a robbery gone wrong. In this touching and compelling novel, he contemplates his life thus far—and his hopes for the future.
7 Steps to Midnight: At the end of an ordinary workday, mathematician Chris Barton finds his car missing from the employee parking lot and a stranger living in his house, claiming to be him. Thrust into a surreal world of violence and mystery, Chris must go on the run, stay alive, and follow a series of cryptic clues to regain his life.