Frozen Kindle

Switch it off and on again. I have far more books on mine and this works when it freezes, although it is very rare. I don't know if a kindle works like a computer with a RAM drive but switching it off will clear the temporary memory and give it a re-boot. It will take a while to start up again when you switch it on, but that shouldn't be a problem.

You switch it off by pressing a little button on the bottom. You may have to hold it for a couple of seconds.

Failing that you can clear some of the permanent memory by deleting books from the device. They will remain in the "cloud" for you to re-download any time you wish.

Oh, I see you say you have tried pressing the button. Did it actually say it was switching off?

When in doubt and nothing else works call into your nearest little independent computer shop I find them a boon

When you hold the power button down you need to hold it until the dialogue box appears asking you what you want to do, then tap ‘restart’. Has this happened? Check on Amazon’s kindle help pages or speak to an advisor. When I had a problem a few years ago they were very helpful. Also just google your issue to find tips. Forty books is nothing for a Kindle - I have hundreds on mine. Hope you get it started soon - I’d be lost without mine. (Well, I wouldn’t as I have the app on my devices, but I love my Kindle)!

Just a tip for later but If you synchronise your Kindle to your phone then you can read your books on either device. I read my Kindle book using my phone as it is much more lightweight, especially useful when reading in bed. I hope you get sorted soon

A neighbour that I help support had this problem. I phoned Amazon.
They were brilliant in putting it right.