Flaws in Lord of the Rings... Yes in the book.

[Keeper of Dol Guldur]

That, is just an educated guess, based on Gollum's double-nature. Smeagol is somewhat nice and was clearly once sort of normal, but the Ring split him into his old self, and his bearer-self, in a way.

I suspect this mirrors Sauron to some extent. While he may not be 'happy-go-lucky' as my sarcasm would imply, he certainly was optimistic and we know for a fact he delighted in some things, like when he had " a mouse fed to his cat" and had it described to him, or when he got a new piece of mithril jewelry (armor, weapon, etc. . .).

The Ring was nothing but cold and calculating.

Slinker and Stinker . . .