Apparently this achievement requires a 100% completion.
simply to say you need 16/16 books read, 33/33 intuition, 16/16 events, 22/21 notes and most importantly 8/8 endings
as well as 4/5 sabot maker way.
so it's best to speedrun your first playthrough on getting all the endings except 'the sabot makers way', 'the truth' and 'the whole truth' in later playthroughs as triggering the events takes time.
i used this useful guide for the walkthrough: http://steamcommunity.com/sharedfiles/filedetails/?id=139422...
as well as the link above for checklist.