Havent seen this listed anywhere. And maybe it isn't an iOS8 thing. But just got the Iphone 6 and restored from backup from my iphone5. I had a lot of documents in iBook like user manuals for electronics, installation manuals for car parts, etc. I just had to save a pdf in iBooks for the first time today and when I very first opened it, I had all of the documents I would have expected. But within a second or two it seemed to shuffle the documents and eliminated a large number of them. Going from maybe 20 total before down to only 4 or 5 now. It didnt even keep the pdf I was trying to add from email so I reopened it in iBooks and this time it stayed. I looked under all the options and they are not there anymore. I need to check my ipad when I get home to see if they are still there. Anyone know anything about this????