Let's start with saying that the authors pull no mathematical punches. They assume a fair amount of maths and use it throughout, and not in the watered-down fashion, so often seen.
Optically, the book is a gem, and the authors have gone to great pains to use all the tricks at the modern printer's disposal.
Despite being, perhaps, somewhat heavy going if you lack the prerequisites, they manage to clarify almost anything for the reader willing to spend the effort.
One amazing thing is, that one does not require a stiff background in chemistry itself. Possible stumbling blocks lie in the maths, and the autors are extremely generous with worked examples and justifications.
A very useful feature is that the reader can cover one of two tracks, the traditional approach and the molecular approach in either order he or she chooses. The molecular approach doesn't start until chapter 8, but if you wish, you can jump in right there and hardly feel a loss not having read the previous seven. (It is heartily recommended that you do anyway -the classical approach is a beautiful subject in its own right.)
So, Mr. Atkins and Mr. de Paula, continue improving your shining work, if you can come up with ways to do so. As the book is now, I imagine new ideas are getting hard to come by, but if someone buys just one book on physical chemistry, this should be it.