How do you obtain the key for the bookshelves, I've done everything possible to find it bit no luck!

Oddly, I don't think that the key actually exists.

I was just actually looking for one an hour or so ago to no avail. I did some reasearch online and it seems that one doesn't exist. I hope that I'm wrong though.

There's no key and they never unlock. PC users can use unlock in the console.
If it makes you feel any better, the cases don't really contain any rare books and the contents of each case are almost identical.

Tyvm! That's what I was wondering and hoping for Rare Books but now knowing that nothing important is in it I'll carry on!!!