I tried uploading over night, 16+ hours, without success. I also noticed bad behavior when trying to Preview this book although it seemed OK if I uploaded it to my web server and downloaded it to my iPad via Safari. I thought I should explore; thinking there may have been a malformed object. I tried deleting chapters and testing preview. I finally decided that maybe it was too 'big' (with over 150 html widgets) and split it into two parts. Both parts could now be previewed and both were uploaded in 1-2 hours.