iBooks and Notes crashing on startup
Same here on an iPad, plus iCloud Drive app was saying I need to enable iCloud Drive, but it's already enabled. 

I managed to fix the iCloud Drive app problem. 


Switch off Settings->AppleId Account->iCloud->iCloud Drive
Reboot
Switch on Settings->AppleId Account->iCloud->iCloud Drive


Nor ibooks nor notes got fixed.

Any hints with ibooks and notes crashes are welcome.