This summer, I read one memoir and three works of fiction concerning World War I, and am now finishing up with a history. I'm in the fourth chapter, and am finding it very clear. The account of the bottomless stupidity of the French War Office in the time leading up to the war is chilling; the other parties concerned were stupid, but the French in charge of planning were way stupider.
Something that may be lacking in this book is some nuance in the description of social conditions within the various countries. Tuchman sketches societies in broad strokes and refers to "national character", and usually depicts populations as if they think in unison. The depiction of powerful individuals and their decisions is better.
This book is suspenseful, marvelously written, and insanely quotable. I can tell that it is not the final word on the causes and principals of the war, but it's hard to imagine a better layperson's introduction.