In this vein, I really recommend "Architecture of Open Source Applications."[1] It's a book series where you learn architecture by example, with each chapter written by a maintainer of the project in question. This lets you learn not only what the architecture is, but what are the constraints that shaped it, usually history and changing project visions.

Not all chapters are equally good or equally interesting, that's the curse of a multi-author book, and all of them are dated, but I think the book is worth reading nonetheless.

[1] http://aosabook.org/