Earth Architecture by Ronald Rael, (Princeton Architectural Press, 2009), which has wonderful photographs and tells you just about everything there is to know about rammed earth as a building material. I was completely surprised by the modern, sophisticated, clean-lined design that this ancient material lends itself so nicely to. Many images show walls that are as straight and smooth as concrete but have the beautiful sedimentary layered look of sandstone, or the wall of a canyon.
I'd love to keep the book, but it's due today at the library (which orders LOTS of terrific architecture books, and pretty much gets anything we ask it to!). – GF