Obligatory question about any and all Mercedes Lackey novels; exactly how much telepathic horse sex voyeurism is there?
File that under things you never thought you'd have to ask.
Depending on when you read through them, you may have missed a couple of Drizzt books that get more into elf psychology. The Hunter's Blades trilogy spends quite a bit of time on the ramifications of outliving basically everyone you know. It's also one of the better chunks of dark elf novel, as these things go.
And if we're not just limited to D&D novels, then the Silmarillion is the obvious and necessary reference. Because the style is very high and historical, it's not immediately obvious, but the sheer amount of time that passes, and the way the elven characters move through that time is decidedly non-human. It necessarily gets into the metaphysics of elves in middle earth, but because Tolkien actually cared about such topics and thought about them, its worthwhile. Rather unlike the fly by the seat of your pants don't think about it approach of the D&D cosmology.