First, be aware that though Amazon currently lists this book as 2008, it is really from 1967 (check the "Look Inside" for the copyright page). I read this commentary cover to cover, but it was many, many years ago, so I apologize that the accuracy of my review is partially conditioned by my memory (though I have it right next to me as I write for quick glances and reminders).
Kidner was a fine scholar who was equally at home with the Bible, the Ancient Near East, and Classical Hebrew. Thus, for the casual reader, he can get you up to speed on much valuable information that will enhance your understanding of the text. Why then, only three stars?
The reason for the mediocre rating is that Kidner's commentary on Genesis is not as helpful as many other commentaries available today on Genesis (e.g., Walton or Waltke). Also, Kidner's commentary on Genesis is weaker than many of the other commentaries in the Tyndale series. Finally, and most importantly, I remember distinctly as I read through Kidner's commentary that as I left each section, I had many questions about the text that Kidner either did not attempt to answer, or glossed over too briefly. This is not always the case. Often after a section, he'll have an excursus that covers certain relevant topics in more detail. However, by contrast, I have been using Walton's commentary on Genesis and find that he seems to know the kinds of questions readers bring to the text and he addresses them quite well.
If only a modern revision could be made of Kidner's work. It could be a real benefit to the Church. Don't get me wrong. Kidner's commentary will give you much help in understanding Genesis. I just think it misses a lot and there are other works out there that are better.