In The Library of Babel by Jorge Luis Borges, the speaker describes the cyclical book as
(The mystics claim that their ecstasy reveals to them a circular chamber containing a great circular book, whose spine is continuous and which follows the complete circle of the walls; but their testimony is suspect; their words, obscure. This cyclical book is God.
What is the significance/symbolism behind the book being "cyclical", as opposed to a different shape?