Deadly Friend

From Author Wars - https://authorwars.com/publications/deadly-friend-368010.html

Overview:

Title: Deadly Friend
Author: Diana Henstell
Year: 1986
ISBN-10: 0553263803
Publisher: Bantam Books
Price: $3.95
Pages: 323
Binding: Paperback
Type: Novel
Title Reference: Deadly Friend
Notes: Data from Amazon.com as of 2011-11-18. Wes Craven directed the film version. Google Books' copyright page: "5 printings through September 1986". Despite being listed as 5th printing, this appears to be first printing under this title & ISBN as it was retitled to match film title.