It gets a little weirder I am afraid.
Yesterday I went to page one of the book I was reading to see if the cover would come back. 2 sleep modes later it did.
Today I sent the book I was reading (in debug mode) several times and it still said Im_reading and it was the only one that said Im_reading in device view. So I sent all of the books that were on a week ago (686).
Suddenly all of the Im_reading books were back. The cover was gone and the square face was back as well.
I opened the book I was reading and the correct cover appeared in sleep mode. I switched back and forthe between 3 books and correct cover came up every time. It was like a miracle.
Shelves
I have 26 pges or approximately 130 shelves. Two shelves had a lot of books. I had made a shelf called All which had all (653) books, so I could sort by recently read. Worked occasionally, but often I had to resort 5-6 times for it to do so.
I removed this shelf and the time to open shelf menu went down to about 25 seconds. I removed the next largest shelf (483) based on a genre column, mystery. The time to open a shelf is now about 13 seconds. Seems excessive still, but much better. I have larger collections and a lot more shelves on other readers and they don't seem to have any problem. Oh well.
Thanks for pointing me in the right direction on the shelf thing
It was like the proverbial lightbulb.
My Mini seems to be much better now. The only things different were running calibre in debug mode and deleting the largest shelf. (The second largest I deleted after the covers were working.)
Thanks again Helen