Comment by jeffreyrogers

Most of these types of books approach things from the wrong direction. Any recommendation should look at the way well designed, maintainable systems are actually written and draw their conclusions from there. Otherwise you allow too much theorizing to sneak in. Lots of good options to choose from and everyone will have their own pet projects, but something like SQLite is probably exemplary of what a small development team could aim for, Postgres or some sort of game engine would maybe be good for a larger example (maybe some of the big open source projects from major web companies would be better, I don't know).

There are books that have done something like this[0], but they are a bit high level. There is room for something at a lower level.

[0]: http://aosabook.org/en/index.html for example.