Four Laws that drive the Universe
Before the Third Law Atkins devotes a chapter to the concept of Free Energy in thermodynamics - a topic which can be confusing, and here the book begins to look a little technical, but its much gentler than you'd find in a textbook. The final chapter on the Third Law looks at the impossibility of reaching absolute zero, and at the phenomenon of negative temperatures
I found that this book was very useful in clarifying the meaning of some of the terminology used in thermodynamics. Atkins keeps away from philosophising about the wider meaning of the subject, and so this book is possibly not aimed at a typical 'popular science' readership. Rather it's for someone who wants to start learning about thermodynamics but finds existing books intimidating.