Volume 10 of HoME, Morgoth's Ring, includes a lot of really fascinating stuff about the Elves, their relationships and 'deaths'. I can recommend that one in particular if you are interested in some of the stranger ideas of Tolkien's. Even so, there's much that still has never been published and occasionally is released as articles in journals, such as the Osanwe-Kenta, about thought transference.
But a lot of my ideas leading on from my reading were conjoured up by talking to davem about it last week! I expounded my theories while he listened patiently.
