"Unable to download item. Please try again later. "

Hello. After updating to iOS8, whenever i turn off and power my phone, I receive a pop-up "Unable to download item. Please try again later. " at first I thought it was an app gone rogue but in the appstore I did not see anything suspicious. After resetting and restoring my device the pop-up kept appearing. By mistake I discovered that if I open the iBooks app the pop-up appears every time. I hace never bought or downloaded any book from here, ever. Did you encounter this error? do you have any suggestions for Me?

thanks