Another possibility, though limiting, is to not navigate away from that library book once it's nearly expired.
I'm not sure all of these precautions are necessary, but this is what I do to keep reading an expired library book:
- Keep the library book as currently reading. Don't navigate away from that book.
- Don't fully shut down, just turn off using the hardware on/off switch.
- Don't connect via USB. Charge using the A/C adapter.
The above is mechanics only, no ethics (like less sales by the publisher to libraries because demand seems less).