I'll tell you one book to NOT recommend: Milarepa. That set me back decades in my practice. Tibetans find the book inspiring and heroic. I find it alarming--and I'm a Kagyu! For that matter keep Naropa and Tilopa out of sight too!
There is a tradition of making a distinction between two different perspectives on the nature of emptiness: one is when emptiness is presented within a philosophical analysis of the ultimate reality of things, in which case it ought to be understood in terms of a non-affirming negative phenomena. On the other hand, when it is discussed from the point of view of experience, it should be understood more in terms of an affirming negation.