Ask HN: Rails Book that explains the inner workings

Hi HN,

I'm a seasoned programmer that is just starting to learn Ruby on Rails. I have a fair bit of web experience (PHP and Python/Django primarily), but I'm totally green to both Ruby and Rails.

I've gotten to the point where I'd be pretty comfortable writing an app with Rails, but I don't feel like I have a good grasp of how things happen; i.e. I can use the provided abstractions, but don't know how the abstractions actually work under the hood. I've started digging through the Rails source, and am documenting my path along the way.

So, two questions:

1) Is there a book or something that explains this well? I've looked through the guides, and most of them seem more focused on "how to use the abstractions" rather than "how the abstractions work" (The "routing from the outside in" guide is a notable exception).

2) If there isn't, would anyone be interested in such a thing?