This is from the my perspective as a basic research scientist and sometimes informal hiker and naturalist who never took zoology or botany too seriously, but on a whim wanted to know more about plant evolution.
This is a wonderful book. It is engagingly written, and more importantly isn't a litany of facts, but rather discusses the topic in the context of biomes, geology, and the evolutionary solutions reached by plants.
One small modification would be useful. Although the book is remarkably jargon free a few more terms in the glossary would have been useful to the non specialist. This said, as a non-specialist I read this book cover to cover and highly enjoyed it.