Of nine parts of speech
Of eight battalions
Of seven stars
Of six rivers
Of five continents
Of four altars
Of three steps
The books "Of two brothers" a "Of one god" are not considered cannonical, because adding them would violate the checksum.
The whole polylogy is sometimes called "Books of Numbers" instead of listing all the numbers, but it has nothing to do with the Plookh¹ set of books of the same name, just as it has nothing to do with the Bible book «Numeri», which is the 4th Book of Moses.
Another possible name is the sum of all seven numbers, but its pronunciation is considered taboo by some.
(1) Plookhkh are seven-sex beings, described by William Tenn in the story "Venus and the Seven Sexes". It is written in their Book of Sevens:
When Plookh meets Plookh, they discuss sex. A convention is held, a coordinator selected, and, amid cheers and rejoicing, they enter the wholesome state of matrimony. The square of seven is forty-nine.
By the way, when speaking of Plookhkh, their religion is worth noting.
“Got a religion?”
“Yes.”
“What’s your belief about a life after death?”
“We don’t exactly have a belief, since no Plookh has returned after death to assure us of the possibilities ahead. However, because of the difficulties we experience in the one life we know and its somewhat irritating shortness of duration—we like to think we have at least one additional existence. Thus, we have not so much a Belief as a Hope.”
“What’s your Hope?”
“That after death we emerge into a vast land of small seas, marshes and mountains. That throughout this land are the pink weeds we find so succulent. That, in every direction as far as an optical organ can see, there are nothing but Plookhh.”
“And?”
“Nothing else. That is our Hope: to arrive sometime, in this life or the next, in a land where there are nothing but Plookhh. Plookhh, you understand, are the only creatures who we are certain do not eat Plookhh. We feel we could be very happy alone.”
The Plookh religion is thus similar to the Bothflench view that religion should be hope and not faith. However, the specific content of Plookh Hope cannot be transferred to the terrestrial environment, because while on Venus the only species which does not endanger Plookhkh are Plookhkh themselves, on Earth, the only species which does endanger humanity is humanity itself.