Try to slide and hold the power button for half a minute or so, then release it - This should restart your Kindle. This is the official solution from the manual I believe.
If it does not work, look at some of the other solutions posted in Screen not responsive, what do I do? There are several (one of them by me) - and one of them should do the trick.
For saving your books, did you try plugging in your usb into a computer? It should recognise your Kindle as external drive, then you can go into the documents folder and just copy your books.
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