n state and federal prisons there is generally no set limit on how many books an inmate can receive or possess at one time, provided the books come through an approved channel such as Amazon or a recognized publisher. Books are considered educational and rehabilitative, and prison systems typically encourage reading rather than restricting it.
The practical limiting factor in a prison setting is storage space. An inmate's personal property is confined to what fits in their locker or designated storage area. Once that space is full, additional books become a property management issue regardless of whether the facility has a formal limit. Sending books gradually over time rather than in large batches is the more practical approach for that reason.
County jails operate differently and the rules are more restrictive across the board. County facilities are designed for short-term housing and have significantly less personal storage space than state or federal prisons. Many county jails limit the number of books an inmate can have at any given time, sometimes to just one or two, and some restrict books entirely depending on the facility's current policy. Calling the jail directly to confirm their specific book policy before sending anything is the safest approach.
One other variable worth knowing is that some facilities require books to arrive directly from the publisher or an approved retailer like Amazon, meaning books mailed from your home address may be rejected regardless of content. That requirement applies to both sending frequency and the channel used, so confirming the accepted method before ordering saves you from a rejected delivery.