Writing system [0]: "In a talk at the Oxford University Society of Bibliophiles on 11 May 2009 [1], Serafini stated that there is no meaning behind the Codex's script, which is asemic; that his experience in writing it was similar to automatic writing [2]; and that what he wanted his alphabet to convey was the sensation children feel with books they cannot yet understand, although they see that the writing makes sense for adults. However, the book's page-numbering system was decoded by Allan C. Wechsler and Bulgarian linguist Ivan Derzhanski, as being a variation of base 21."

[0] https://en.wikipedia.org/wiki/Codex_Seraphinianus#Writing_sy...

[1] I could not find a source for that talk

[2] Automatic writing, also called psychography, is a claimed psychic ability allowing a person to produce written words without consciously writing. https://en.wikipedia.org/wiki/Automatic_writing