It’s an entire shelf of books and notes about a world known as ‘Creation’. This is pretty much the sum of everything he knows about home, so there’s a lot if she decides to peruse them.

Some things of note:
The world is understood to be flat. The celestial bodies of the sun, moon, and the planets (stars) are also deities of the highest order, known as the Unconquered Sun, Luna, and the Five Maidens. The Maidens in particular get a few extra notes, and the distinction of probably the only use of coloured pigments out of all the writings here:

Mercury, Maiden of Journeys - beginnings, travel, roads, messages
Venus, Maiden of Serenity - joy, love, the arts, worldly pleasures
Mars, Maiden of Battles - conflict, tribulations, endurance, resilience
Jupiter, Maiden of Secrets - knowledge, perception, wisdom, foresight
Saturn, Maiden of Endings - change, inevitability, death, upheaval

There are notes about Chosen, and also about the Immaculate Faith, though given how the latter is kind of just shoved into a corner of the shelf, you get the impression it isn’t something that is thought of with fondness.

There’s a whole sub-section for Wu-Jian. In fact, it takes up half of the shelf, easily.

Besides that, information about Shrike, Persephone, Amaranth, Sashay and Tatsuo can be found on the shelf.