You have a first edition hardback if there is an $8.95 price on the upper inside front of the dustjacket, a typographical error crediting Koontz with a novel entitled "The Hanging Man" on the lower inside rear of the dustjacket, and "First Edition" stated on the bottom of the copyright page.
You have a paperback first edition if it has the number series "10 9 8 7 6 5 4 3 2 1" beneath "Printed in the United States of America" on the copyright page.