Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Misanthropic (i.e. Man-hating)
Have you noticed that Machiavelli seems to think that most people are idiots? Not us, because we're awesome, but you know, normal people. The way that Machiavelli talks to the ruler he's addressing is like he's saying, "Look, I know you are awesome, but these people you're leading are dumb as rocks, so you have to force them to do what you want them to."
Men are so thoughtless they'll opt for a diet that tastes good without realizing there's a hidden poison in it. (13.6)
Although that's an eerily prescient commentary on the obesity epidemic, it's also just plain mean. Then later, he just comes out and says it: "People are so gullible and so caught up with immediate concerns that a con man will always find someone ready to be conned" (18.3). The nerve.
Now that we got you all riled up, it's time to calm down. We really think the better word for this part of Machiavelli's tone is realistic. In Machiavelli's day, everyone was writing this kind of book, but most of them were idealistic about it. In their world, clouds were made of marshmallows and it never rained when you wanted to go to the beach.
Machiavelli was tired of these books, and this tone is his way of saying that he's not playing around. He's taken off the kid gloves and brought out his boxing gloves.
The dedication and the last chapter of the book are hard to stomach. Machiavelli is just on his hands and knees in these sections, begging Lorenzo de' Medici for mercy. It's not a good look for him. Who wants to see Iron Man cry? No one. The tone of the book goes from the dry, know-it-all voice that we talked about above to a whiny, annoying, suck-up. This sort of praise and language was standard form when talking to anyone as fancy as Lorenzo, but to our modern ears it sounds sickeningly sweet.
Just look at how Machiavelli humbles himself and The Prince: "this gift is no doubt unworthy of you," and, "Nor, I hope, will you think it presumptuous that a man of low, really the lowest, station should set out to discuss the way princes ought to govern their peoples" (1.2). Finally, he tops it off with, "Then if, from the high peak of your position, you ever look down on those far below, you will see how very ungenerously and unfairly life continues to treat me" (1.3).
Essentially he's saying, I know my book is terrible, and I'm really silly, but maybe you could just rub a teensy tiny bit of your awesome on me, and scratch my belly while you're at it. Maybe.
This trend continues in Chapter 26:
What I can't see is any family the country could put its faith in right now if not your illustrious house, blessed as it is with fine qualities and fortune, favoured by God and the Church - actually running the Church, in fact - and hence well placed to lead Italy to redemption. (26.3)
In other words, he says, you guys are the best—even God thinks so. In fact, he uses the same word, virtù, to describe the Medicis as he used for all his examples of rulers that were awesome.
This sort of faux-humility and flattery was meant to warm the heart of Lorenzo de' Medici. Maybe. Maybe it was a middle finger to the family that kicked him out of his dream job. Who knows? Anyway, whether The Prince warmed Lorenzo's cockles or not, no one knows. No one even knows if he read the book that was probably heaped with all his other presents of gold, jewels, and horses. If Machiavelli had dedicated The Prince to you, would you have been won over?