The Star Wars Trilogy

From Author Wars - https://authorwars.com/publications/the-star-wars-trilogy-296484.html

Overview:

Title: The Star Wars Trilogy
Author: George Lucas, Donald F. Glut, James Kahn
Year: 1997
ISBN-10: 1568654359
Publisher: Del Rey / Ballantine / SFBC
Price: $14.98
Pages: 500
Binding: Hardcover
Type: Omnibus
Title Reference: The Empire Strikes Back
Notes: First hardcover edition
SFBC ID #17284 (printed on the back of the dustjacket).
Info from Locus1, who gives the month of publication as September.