I tend to agree with the "ADHD"-"undigested thoughts" analysis of the book. It's clear that Ries has some extremely innovative ideas about startups and has perhaps invented the best method of idea validation. However, he seems to have learned to write from a generation of bloggers who can organize a collection of paragraphs for poignancy, but have no idea how to organize chapters for understanding.
Still, you don't read this because Ries has mastered the pen, but because he's developed a system that will eliminate waste from your startups.