Widely studied as the author of ThePrince (http://www.constitution.org/mac/prince00.htm), a discussion of how to rule a principality.  But typically not considered as a HowTo RunAnyCountry 101 textbook.

Can fairly be regarded as a classic.  Along with MrPlato's TheRepublic, forms the foundation for a modern PoliticalScience curriculum.

Machiavelli also wrote a similarly brilliant treatise on how to run a republic, called DISCOURSES: Upon The First Ten (Books) of Titus Livy(http://www.constitution.org/mac/disclivy_.htm) often shortened to DiscoursesOnLivy.

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The term "Machiavellian" has very negative connotations of ruthless manipulativeness, far more than seems justified from the content of ThePrince.  (Though "machiavellian" also implies the necessary intelligence and guile to carry it out, so it's not ''entirely'' an insult)

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I can thoroughly recommend 
The Portable Machiavelli by Niccolo Machiavelli, Peter Bondanella (http://www.amazon.com/exec/obidos/tg/detail/-/0140150927/102-1198435-8390534?v=glance). Machiavelli saw the top and bottom of the political life before he wrote his major works, so it is by no means theory, nor bereft of understanding of the common people.

As I understand it, Machiavelli illustrates incisive pragmatism, in a similar way to SunTse (TheArtOfWar). He reached his deductions from studying the politics of ancient civilisation (mostly the classics of Greece and Rome), and the recent history of late-medieval/early renaissance Europe and Asia. He does emphasise that a successful leader will not have the luxury of treating people in a pleasant fashion, as they compete with everyone else that wants a piece of the pie. 

Machiavelli actually thought that the best power structure was the Roman Republican system, with balance between the people and nobles through a few layers of officials (appointed by both parties), and transparent legal processes.

His writings also give you an appreciation of how effective the old curriculum subjects of rhetoric and classics could be in allowing young men (given the times) to take and hold empires. 

WillChamberlain