Aziraphale immediately perks up the moment she says the books can be upon request. Oh, he misses his bookshop so, and it's not like anything could ever replace it, but he now has a great interest in this option.

He carefully takes the books, opening and flipping through one of them, looking genuinely fascinated. "A catalogue, you say?" He looks at her again. "Do we just get the books? Or is there some sort of trading system?"