The Door into Shadow

From Author Wars - https://authorwars.com/publications/the-door-into-shadow-38600.html

Overview:

Title: The Door into Shadow
Author: Diane Duane
Year: 1984
ISBN-10: 0312941102
Publisher: Bluejay Books
Price: $7.95
Pages: xii+298
Binding: Trade Paperback
Type: Novel
Title Reference: The Door Into Shadow
Notes:
"First Bluejay printing: April 1984" No printer's key. Price on back cover and spine. ISBN and LCCN stated in the CIP data. "Cover and foldout art painted by Susan Collins." on back cover. Map artist credited below the bottom border of the map. There was an announcement for a signed limited edition of 500 hardcover copies ($40.00), but research has found no evidence that it was ever published. Internal art is a color fold-out drawing between pages 148 and 149. In-universe essay (p. 297) "On Dracon Anatomy and Physiology".