I took my iPad 2 (64GB wifi) into the Apple Store in Bristol this morning for an appointment at the Genius Bar. Fortunately I was able to demonstrate the problem to the Genius (wish they'd use another word) using Safari and iBooks. I had been catching up with the news then switched back to iBooks. The book promptly closed and reopened - the usual thing.
Unsurprisingly, he'd not come across this problem before. His best suggestion was to do a DFU restore which I believe restores the firmware before installing iOS. This does of course mean losing all apps and data. After some debate (I had backed up the iPad yesterday evening), I decided to take one for the team and we went ahead and did the restore.
I now have a pristine new iPad with a bare minimum of apps. I downloaded iBooks and restored a book then used Safari for a bit then went back to iBooks. The same problem ... it was all for nothing.
BTW, I was having a coffee in a cafe just before the Apple Store appointment and when I swapped to iBooks there was no close/refresh behaviour, i.e. this is not purely a time dependent issue as the iBooks had been pushed to background over an hour previously. Only once I was in the store with a wifi signal and used Safari for a while did the problem reoccur. Could Safari be the common link? Is anyone having this problem who does not use Safari?
The Genius did take down all the details and logged it as a support issue with Apple and advised me to do the same if the DFU restore did not solve the problem. I might suggest all of you do the same.
So, even the most extreme reset failed to solve the problem. We are still none the wiser. I just hope my app and data restore goes OK ...