I liked this landscaping book more than some others I've read, mostly because they can be applied to city lots, and not just larger, rural lots. The twelve principles of landscaping he lays out are divided into two sections of 6. The first 6 are structural, and the second 6 are aesthetic. The structural principles are fairly typical of most other theories of landscaping, although he focuses on the creation of "rooms" as the basis. (Other designers usually mention "garden rooms", but leave this more open-ended. I found it helpful in breaking down what could be a very large project into manageable chunks, as well as being an aesthetic inspiration.) It wasn't mentioned in the book, but an easy way to try to see where natural boundaries for the "rooms" are is to get on Google maps and find a satellite view of your property. It is easier to identify the strongest defining lines from that angle, and existing trees and shrubbery.
It is written in a narrative style, and is a bit wordy at times. There are briefer ways to summarize these principles, buy it's a matter of opinion and taste as to how important each one is, or how to apply them to any given garden. He sprinkles little ideas throughout the narrative. I particularly liked his inclusion of "mystery" as one of the aesthetic principles It was enlightening to read about obscuring and screening views, as I had not thought of this. I like his aesthetic style overall, although we disagree on the value of the color Orange. He refused to write much about using the color orange in the Color section, but went on and on about other colors that he liked more. He is very opinionated on some points. If you agree with his aesthetic, fine, and if not, you may find this quirk annoying.
If you like P. Allen Smith's English-garden-inspired aesthetic this isn't a bad choice for an introduction to landscape design. There are lots of pictures and ideas from his own garden on a city lot, as well as other gardens that he admires.