After a series of complaints,

I have re-designed the Magician's Tome into the Spellcaster's Codex.

More portable but less robust.

The Spellcaster's Codex

The Spellcaster's Codex is essentially a book, consisting of one quire (8 pages, 16 sides) of vellum folded together.

The folded vellum is cut to form the 8-page, 16 side booklet.
The books are fairly thin, about A4 and take a whole hide of goat or sheep to make.
The book is then usually put inside a leather cover, although velvet-covered wood is sometimes used.
This book is then inserted into a leather cover and tied up with thongs or reed.

Lightweight and portable