Books reference each other, directly or indirectly. You can now spend a life spidering from one book to the other.

Are there starting points? Certainly, the Illiad, the Epic of Gilgamesh and more.

At some points in the history of litterature there has to be books that bridge between the Illiad and the I Ching (even before the Man in the High Castle).

Then, all those who toil away at writing new books that echo the voice of the old bards.