[Epic] Intro and book material to present to potential publishers

[binkley]

Related stories: #494, #521, #540
Remove the "P0" priority marker: it messes up sorting in the card wall.

Context

The key objective for is that we can approach publisher with this as book material. The first things folks see is the introduction and related materials. Focus on making this as solid as makes sense for a book undergoing rapid changes.

Acceptance criteria

(Not in given-when-then format)

We are OK with presenting book material to potential publishers.