Geis of the Gargoyle is the eighteenth book of the Xanth series by Piers Anthony.
Golem in the Gears is the ninth book of the Xanth series by Piers Anthony.
Harpy Thyme is the seventeenth book of the Xanth series by Piers Anthony.
Heaven Cent is the eleventh book of the Xanth series by Piers Anthony. It is the second book of a trilogy beginning with Vale of the Vole and ending with Man from Mundania.