The Book of Thoth was published in 1944 as an issue of Crowley's serial The Equinox, in a small subscribers' edition, and it exists because of the deck. Crowley and Lady Frieda Harris had spent five years on the paintings, a project originally expected to take three months, and the book is his exposition of what the cards were built to carry.
Its contents are correspondences and argument rather than divinatory meanings. Crowley sets the trumps against the Hebrew letters, the elements, the planets and the zodiac following the Golden Dawn scheme he inherited, explains the changes he made to it, and defends each. The best known change concerns the letter Tzaddi and the trump named The Star, which the atlas treats on its Path entity, and the second is the renaming of several trumps.
The book also contains his method of divination with the deck, which is unusually demanding and is not the method most users of the cards employ.
Harris is properly a co author of the object even though her name is not on the spine, and the deck as it is actually used owes as much to her painting as to his scheme. She was still working on the plates when the book went to press.
The subscribers' edition was bound in Morocco leather and limited to two hundred copies, and Crowley did not live to see the deck itself printed. The cards were not published until 1969, more than twenty years after his death and Harris's work on them.