What's a good introductory book to political philosophy?

This one looks like it would fit the bill.

Why read about them? Why not start with primary sources?

The Republic by Plato is probably the place to start.

This list from Wikipedia will give you more writers to look for.

Here’s another

@janbb
Um are you sure its as I described?

Not exactly but it was the closest I could find. If you go to Amazon and put in keywords “political philosophy” you can comb through the listings yourself.

http://www.amazon.com/Introducing-Political-Philosophy-Dave-Robinson/dp/1840467606/ref=sr_1_2?s=books&ie=UTF8&qid=1349651550&sr=1-2&keywords=Introducing+Political+Philosophy

Is a good example but I would like something a little bit more in detail

In my opinion, the best introduction to political philosophy currently on the market is A. John Simmons’ Political Philosophy. It does not follow the format you are looking for, however, as most political philosophers would contend that no good introduction to their subject could follow such a format while also providing sufficient detail. The Robinson book you linked to is an example of the limitations of your desired format. That’s why most choose to adopt a topics-based approach instead.

If you were interested in a chronological anthology of classical readings, then my recommendation would be Alan Ebenstein’s Great Political Thinkers: From Plato to the Present. You’ll need a bit of luck finding a copy at a decent price, though. Alternatively, you could try Steven Cahn’s Political Philosophy: The Essential Texts or a pairing of The Cambridge Companion to Ancient Greek Political Thought and Modern Political Thought: Readings from Machiavelli to Nietzsche.

After following @Hawaii_Jake‘s suggestion of The Republic, read The Prince by Machiavelli.

Candide, by Voltaire. Really.

@CWOTUS Quite so. Candide is an excellent introduction to almost any area of philosophy when it comes right down to it!

I would suggest Ameritopia by Mark Levin. It is a book about how the founding fathers came up with the system of governance we have in America and what the prominent political philosophies were at the time. It’s a good read and quite informative. I recommend it highly.