This book is very, very good and the second half is very advanced but covers 'classical' statistical mechanics. There is no discussion of modern methods such as RG, mean field theories, magnetic/spin systems, critical phenomena, etc.
But it covers classical liquid theory, imperfect gases, brownian motion and time correlation functions better than most books I have seen. In particular, it covers classical liquid theory in more detail than I have ever seen.
Anyone who does stat mech should probably have this text, but it is dated.