The intro seems short to me, maybe because I vaguely remember agonizing over writing it a few short years ago. There are only five segments; in the physical book, the introduction is only nine pages. Online, it is just five.
But it says what it needed to say. The difficulty in writing it, originally, was in deciding what to leave out; what to save for later. That was where having written a book proposal came in really handy. I trusted my outline.