I'm exceptionally irked about what happened to my iPad when I upgraded to iOS 11... I keep my sermon manuscripts in iBooks, and I use my iPad instead of printing out my messages each week. (Years ago I was one who pontificated about the superiority of keeping my manuscript as a printed document, but, it turns out that I was an unwashed Philestine, content with making mud pies in a slum when a holiday at the beach was offered to me... now, my eyes have been opened, and my sermon delivery has been dramatically aided by having my messages on iPad rather than on paper!)
Anyway, I woke up the morning after the update to iOS 11 and opened iBooks to discover that my entire library of documents I'd added were GONE. Fortunately, I store the documents in Dropbox, so I didn't truly lose all my past sermons, but still - they are GONE from my iPad.