If you want a good book on Macroeconomics, I'd suggest Krugman's instead (or perhaps in addition to this, to compare viewpoints).
Paul Krugman is much more balanced than Mr. Barro. Don't believe me? get both books and judge for yourself. Krugman's book is available at:
http://www.amazon.com/exec/obidos/ASIN/0321033876/
Barro begins with a survey of the United States economy, the history of all the standard macroeconomic variables, and the micro foundations of macro analysis, including such staples as the permanent income hypothesis, labor as a choice between remunerated work and leisure, and utility maximization. From this springboard more complicated phenomena like business cycles, capital markets, money and banking, inflation, and government intervention can be understood. The book culminates with a dressing-down of the Keynesian model's explanation of responses to external shocks and a demonstration of the advantages the neoclassical model has in explaining such shocks.
All the while, Barro takes the time to show how empirical evidence stacks up against theory, with much drawn from his own seminal work. He does not belabor the reader with excessive mathematical formulations; usually some shorthand equations are sufficient to explain which variables are involved, and whether they are related positively or negatively to the result. He is also adept at translating mathematical into diagrammatical analysis--a real boon, since any good economist must be adept at both. Why wait until graduate school for that?
Unfortunately, the book occupies that awkward purgatory between an intro principles book and a rigorous upper-level text replete with explicit theory and mind-numbing equations galore. So it is an excellent "intermediate" macroeconomics text which will hopefully be supplemented in lecture by a responsible professor. Responsible enough, that is, to not be ashamed of neoclassicism (unlike a previous reviewer crying 'ideologue') and to give his students a thorough exposition of the (for better or for worse) leading paradigm in economic analysis.
Law Ka Chung