The road to splendor is but an empty dream. What truly matters is the people you've met along the way - your friends and family - and staying true to yourself, to them, and to all that is good in the world.
I haven't read the novel in detail, just skimmed. And I can't find book 5 except for someone's audiobook they made of it lol. It was so long that I couldn't finish it. But no mention that I know of of him being a demon or anything of that sort. Of course, maybe the writing team have knowledge or have talked to the original author since the 6th book is currently being written.