How to alleviate back pain from study or working on computer in public places frequently?

Taking regular breaks might help. Also, stretching. Just raising your arms above your head and linking your fingers and stretching up can reset your spine to a degree. Breaks are really the key though. Even if you just walk up and down for a few moments. Push your shoulders back. The muscles of the back lengthen and those in the chest shorten, so trying to counteract this is helpful.

Also, make sure your work area is set up properly. Even if you have to use books to put your laptop on (if you have a laptop), feet firmly on the floor. So you aren’t hunching over. Lower or raise the chair. I know you are in a public place, but as much as you can set up where you are working so you aren’t putting strain on your back.

Can you take a small pillow for your low back with your books?

Back support wrap bandage- supposed to help keep better posture.

Donut seat cushion- eases lower lumber stress which eases pinch sciatic nerves.

I’ve got a newly discovered back problem and my job of sitting for 10+ hrs at a time makes this sketchy. I’ve tried different chairs, different chair heights but the silly donut is working the best. I wrap it inside a pillowcase.

Purchase a back support from a home improvement or medical supply store and a cushion as suggested above.