This is the book to be read. There's no reason to hesitate, neither to read the commentaries to decide. As far as books of prehistoric animals are concerned, those of dinosaurs occupy most of them. And maybe this is the first, and the best I insist, to be written on the primitive form of tetrapods. Detailed investigations show us before and after the first members of tetrapods including their environmental conditions, soft tissues such as respiratory, sensory and reproductive systems and interpretation inferred based on the existent animals whose morphological character is insinuating. And, of course, their relationship analysed by cladistics comes in later chapter.
The most important point the author puts emphasis on is to urge our public image or concept on the early members of tetrapods. She intentionally avoids the word "amphibians" for them. You'll see why through the text. This is a superb book! Why don't you take a close look at their intriguing story?

Gaining Ground: The Origin and Evolution of Tetrapods written by Jennifer A. Clark is a book on comparative anatomy of tetrapods on Earth.

The origin and evolution of tetrapods started about 370 million years ago, something strange and significant happened on Earth. That time, part of an interval of Earth's history called the Devonian Period by scientists such as geologists and paleontologists, is known popularly as the Age of Fishes. After about 200 million years of earlier evolution, the vertebrates... animals with backbones... had produced an explosion of fishlike animals that lived in the lakes, rivers, lagoons, and estuaries of the time. The strange thing that happened during the later parts of the Devonian period is that some of these fishlike animals evolved limbs with digits, fingers and toes. Over the ensuing 350 million years or so, these so-caled tetrapods gradually evolved from their aquatic ancestry into walking terrestrial vertebrates, and these have dominated the land since their own explosive radiation allowed them to colonize and exploit the land and its opportunities. The tetrapods, with limbs, fingers, and toes, include humans, so this distant Devonian event is profoundly significant for humans as well as for the planet.

This book tells the story of the evolution of tetrapods from their fish ancestry and puts the sequence of events into its ecological context. The story if founded on an understanding of the evolutionary relationships between tetrapods and their fishy relatives... their phylogeny... and traces the family tree of tetrapods from its roots to the point at which the major groups of modern tetrapods branch off from its original trunk. The tetrapod family tree is in fact more like a bush, with several main branches, some of which have died out during the course of evolution and some of which have become large and important from small beginnings.

This book looks at the changes that occured in the transition from creatures with fins and scales to those with limbs and digits in an attempt to understand how, as well as when, these changes occurred, and to do this, it is necessary to understand something of the anatomy of the animals involved. Chapters 2 & 3 are devoted to these parts of the story. Chapters 4,5,& 6 set out what is currently known of the earliest tetrapods and their lifestyles. By careful analysis of what is known of them from fossils, and by comparison with modern animals that live at the transition between water and land, it may be possible to understand a little of how the early tetrapods worked as animals. After the tetrapods had become established, they radiated into a ranges of forms requiring modification of the original tetrapod pattern. Chapters 7,8,& 9 carry the story forward from the origin of tetrapods to their ultimate conquest of terrestrial living. The final chapter drws together some of the threads that have been taken up in the preceding chapters and shows how they impact the study and understanding of tetrapods today.

All in all, this is a well- written, illustrated, and organized book, making for a fairly fast read even though there is a lot of material covered. Devonian environment and the timing of anatomical changes was fascinating.