"Since the device is a light bulb, it would be difficult to detect and likely to go unnoticed."
I doubt it would be any harder to shut down than any other public-access WiFi device, just a bit of experimentation with turning off power / devices would find it.
Modern enterprise access points even have built-in functionality to physically locate devices, and automatic warnings for rogue access points. The latter is often ignored or disabled though, because it'll go off every time someone prints or screen casts over Wi-Fi Direct.
If you went the other direction and didn't worry about it being noticeable, it would be kind of a fun project to break up a book into a series of QR codes. A scavenger hunt, with each code's text ending with a clue of where to find the next?