It ranked number 5 in the Science Fiction & Fantasy category on The Independent on Sunday bestseller list.

[1] The book begins with Cornelius hired by the mysterious Arthur Kobold, who claims to represent a publishing firm wishing to print a complete copy of The Book of Ultimate Truths, a set of great secrets discovered by Hugo Rune, but suppressed by unknown forces.

They encounter the evil Campbell, who is also seeking to retrieve the lost book, to allow him to return to the Forbidden Zones, areas of the world hidden from humanity (excepting London taxi drivers).

Cornelius and Tuppe pursue him to the nearest entrance to the Zones, but the Campbell's plans are foiled by the arrival of a large gathering of a cult devoted to Hugo Rune.

Arthur Kobold presents Cornelius with a large cheque as an advance against royalties from the publication of the book.