Although this does not seem to have been the author's intention, this book is an excellent introduction and overview of Sparta. In slightly more than 200 pages and plenty of well drawn maps and shematics for Sparta's major battles, Scott Rush has produced a very good summary of Sparta's military history. Although the book contains the date 550-362 BC, it also presents what happened before and after.
In fact, and to a large extent, this book is also a summary of the main conflicts over a period of about 200 years. Unsurprisingly, 2 and 3 chapters are devoted to, respectively, the War aganist the Persians and the Great War (or the war against Athens, as the Spartans called it with the Athenians calling it the war against the Peloponesians). I particularly enjoyed the last four chapters from 404 to 362 BC, the period of domination and Fall, simply because it is usually less well known and less studied. There are some very interesting developments on Theban tactics and their impact on Sparta. The limits to Sparta's power and the importance of Messenia are also clearly shown, but the importance of Argos as the secular rival is also emphasized while the other cities could be either (more or less voluntary) allies or adversaries, depending on their interests.
One limit of this book is that the discussion on "oliganthropia", its causes and its effects on Spartan armies are a bit on the "light side". Since this is one of the key reasons for Sparta's ultimate demise, this is proably a weak point. To learn more on this, read Cartledge's book (and "Agesilaus and the Crisis of parta", in particular).
Another limit of this book is perhaps that it is mostly focused on campaigns, battles and tactics, with the larger picture (diplomatic ties, politics etc...) being less developed. One example is the rather shoprt piece on the period between the end of the Persian Wars and the beginning of the Great war between Athens and Sparta. Also, the outbreak of the Peloponesian war could have been better covered. For those wanting to learn more on this, Donald Kagan's first volume that bears this very title (of four) is a must. In particular, Kagan shows very convincingly in my view that neither Sparta nor Athens wanted to go to war initially, but that they were dragged into it by their respective allies.
Anyway, this is certainly not "the definitive work on the subject", as the other reviewer claims. However, it is a rather excellent introduction to Sparta, and to its main claim to undying fame: War. Not perfect perhaps, but certainly very good.