Now I do not know, whether someone has experienced a similar issue, but I am currently playing the "At the summit of apocrypha" quest, which at this moment requires me to grab the "Boneless Limbs" book and then I can proceed through the open door... Problem is, that I accidentaly opened this black book earlier, grabbed the Boneless Limbs and did not continue on, instead I returned to Soltstheim. Now I have this as a quest, there is no book seeing as I already have it and the door is LOCKED!!! and behind it, there is another book on the table for me to use and continue... ANY HELP?! and I know that there is a solution which requires me to load an earlier save but that would mean to replay "The Gardener of men", "The Path of knowledge" and "Cleansing the stones" quest which is ridiculous cause these quest took me like 2 days of average play time to finish... Any help on this is greatly appreciated BTW bethesda, this DLC ROCKS!!!!!