The two books that began the "Feline Wizardry" sequence -- The Book of Night with Moon, and its sequel, published in the United Kingdom as On Her Majesty's Wizardly Service and in the US as To Visit the Queen -- are offshoots of the Young Wizards series, taking place in the same universe, and featuring occasional crossovers of characters from the older, larger series.

In the YW universe, it's understood that wizardry is sometimes offered to Earth-based species besides humanity if they are either intelligent enough, or just high enough up their local food chain. Cats qualify on both counts: any animal smart enough to routinely get humans to give it food for nothing will plainly have no problem mastering wizardry.

Additionally, in the YW universe, cats have a unique talent for easily seeing things invisible to most other species without special aids -- such as the hyperstrings and associated structures on which worldgates are hung. Cats who've qualified as wizards therefore frequently find themselves working in worldgate maintenance and repair. This is the business of the cat-wizards whose stories are told in the "Feline Wizardry" sequence.

The first book of the sequence was published as a hardcover by Hodder & Stoughton in the UK in 1997, and was followed later that year by a trade paperback US edition from Warner Aspect Books. The second book came out from Warner, again in trade paperback, in 1998, followed by another hardcover edition from Hodder in 1999.

A third book was always planned. When neither publishing house exercised their option to buy it, Diane Duane turned her attention to other projects. But now it turns out that this was not going to be the end of the story...