Half Magic

From Author Wars - https://authorwars.com/publications/half-magic-391271.html

Overview:

Title: Half Magic
Author: Edward Eager
Year: 2000
ISBN-10: 0192750984
Publisher: Oxford University Press
Price: £4.99
Pages: 182
Binding: Trade Paperback
Type: Novel
Title Reference: Half Magic
Notes: Format: Illustrated. Edition statement: New edition. Data from Amazon UK as of 2012-06-26.

Page count and Bodecker illustrations from British Library (BL, below) which confirms data including price £4.99. Cover illustration is that by Blake for the 1999 Odyssey/Harcourt editions (relying on Amazon for this cover image).