I may be mistaken here, but I think Patrick may be referring to the library of Stripe Press published books, which are available internally (and externally, if purchased)?
"Stripe is a celebration of the written word which happens to be incorporated in the state of Delaware. We produce prodigious amounts of it internally, most of it widely visible within the company." - https://www.kalzumeus.com/2019/3/18/two-years-at-stripe/