Recently Reading: Design in Nature
The book provides a very good general introduction to constructal theory. This is the best book I've read in ages.
The main idea is that everything in nature, including us, grows in the quality of its flows, according to a physical law. This resembles and complements thermodynamics. Despite the abstractness of the idea, it has relevance throughout realms of everyday life.
I think this is the most beautiful idea I've ever come across.