The Bexar County Sheriff’s Office has put out information on sending books to inmates. The below is from the official BCSO website.
Inmates are authorized to receive publications such as three (3) PAPERBACK books (three (3) per week, per inmate), magazines, and newspapers as long as they come direct from a publisher or an established bookstore. The inmate’s SID number MUST be on the shipping label, if not, it will be returned to sender. All paperback books must have a PERFECT binding.
Any publications from family, friends and internet sites are prohibited and all items will be returned to the sender. All third-party book vendors are prohibited. Adult magazines such as Playboy, Hustler, etc. are strictly not allowed.
Amazon Book Deliveries
You may order books from Amazon, but they must be delivered by a public carrier (US Postal Service, UPS, or FedEx). Do not use Amazon Same Day delivery that uses a contract carrier or your order will not be accepted; it will be rejected and returned to sender.
Note that it says the inmate’s SID number MUST be on the shipping label. Also, pay attention to it saying that the book must have a perfect binding. I suspect used books could cause issues with that section and would recommend that you only purchase new books. I doubt they would consider Ebay as falling into the bookstore category no matter how big Ebay is, so I would stay away from them especially since they do sell used books.
When they say third-party book vendors are prohibited, they mean those book sellers you can use when you click on Amazon’s other options such as a “used” version of the book. Or books that are new, but have the book listed at a different price than Amazon. Basically, if the “Shipped from” is something other than Amazon, they are a third-party vendor and will be rejected.