Arranged in sections and by nation, this book provides a comprehensive review of every major class of submarine from all navies of the world. Each entry gives specifications, followed by development and battle histories where relevant.
Fairly interesting ... if you like submarines. I do, so yeah. It's got detailed tables with technical specifications and weaponry, nice photos plus a brief history for each listed model. Good stuff for technophiles.
Illustrated Directory of Submarines by David Miller is a small survey work examining production naval submarines largely from the WWI era onwards. Although billed as a work covering submarines from the Civil War era onwards, this work only gives a nod to those early machines and it will be difficult to find where they are mentioned. If you are looking for the groundbreaking work of submarine pioneers like Simon Lake, or prototype or unfinished miliary subs like the German U-cruisers of the 1930s, you'll need to look elsewere.
Miller does well in covering military subs and given the confines of a trade paperback, he does include photos, tables, and some illustrations. Well-known military subs from the worlds navies are described, though not in the detail I would have liked. Major ship systems and weapons systems are detailed but not described, and at times I found myself yearning for other reference works in order to flesh out his descriptions.
Miller's work while very useful should not be the only submarine reference on your bookshelf.