Keeping to the original theme of the abstracted, never-present antagonist, I'm going to take the mention of Sauron/Jordan's Dark Lord and Big Brother, and from there propose that there are many books that fit this model.
These super-antagonists are embodiments of ideas. They are societal evil given shape. In some cases, they are the embodiment of an enemy of the society the story is set in, but - probably more often - they represent a perceived evil of the real world. That evil may be something attacking the accepted structure of society, or it may be a cancer within society itself, depending on the author's perception. (For example, it may be a representation of those who anjure a dominant religion, thereby undermining the accepted order; or it may be a representation of the religion itself that restricts and represses the individual.)
These enemies, these evils, are too large to be faced head-on. As antagonists, they cannot be conquered directly. Therefore, the story will revolve around the protagonist's interaction with an avatar of the great enemy. In the case of Big Brother, O'Brien is that avatar. In the case of Sauron, it's the Nazgûl. (Yes, in the case of LotR, Sauron himself is defeated when the ring is thrown into Mount Doom, which would say that he is actively present throughout the book as his soul is forged into said ring… but let's leave that as a cheating device to achieve absolute victory in a situation where it shouldn't reasonably be possible.)
Yes, much fantasy - at least from a certain period - was built upon this simplistic good-versus-evil theme, with a great enemy that could not be faced directly, pitting heroes agaisnt the evil's avatars.
And there is another genre where this is near ubiquitous: historical military fiction, specifically in an Allies-centric, European WWII setting. Hitler - or the Third Reich - is the ultimate antagonist, the real enemy. The German forces, whom the protagonists come in contact with, are only avatars. Puppets.
I'm sure that there are other genres that follow this same archetype.