It's not hard to see why this is considered so important. He goes one step beyond Machiavelli and just totally blows apart the last remaining shreds of virtue-derived political praxis. Politics no longer has anything to do with the idea of 'the good,' what we have now is a secular system in which we consent to have rulers to protect our own interests, however noble or terrible they may be, because without that framework we'd just live like animals, fighting absolutely everything else in the world for resources. Sure, it's pessimistic, if you had lived through a civil war in which 1/10 of your countrymen had been killed, how positive would you have been? Some of it's a bit creepy, like his notion that you can't legitimately criticize the sovereign, etc. The biggest obstacle to this is his writing style. This has to be one of the driest texts of any kind I've come across. He exhaustively clarifies absolutely every assertion, and usually offers some kind of addendum for each clarification. If you think Aquinas and Aristotle are too sloppy, this is probably to your liking. Personally, I found it hard to stay awake for large tracts of it.