The Prince is a 16th century treatise by Niccolo Machiavelli advising rulers how to gain and maintain their kingdoms. The document outlines different strategies for conquering societies and dominating their political systems. Machiavelli's outlook is notoriously pragmatic and hard-hearted. The second half of the document describes favorable qualities for rulers, claiming that it is safer to rule by fear than by love, to withhold rather than to be generous, to be cautious and crush power-hungry flatterers and conspirators.
Boasting the largest collection of book summaries, BookRags is the best option for titles you can't find elsewhere. They offer all of the basics (quotes, chapter summary, characters, historical context, literary criticism) but also walk through a few major topics that recur throughout the book, which can be particularly useful for essay writing.
The original provider of professionally-written study guides, Cliffs Notes were available in print form before the Internet even existed. Their content is very comprehensive and includes an analysis of characters, detailed chapter by chapter summaries, critical essays, essay topics, and many other sections.
Their book summaries aren't as good as other providers, but PinkMonkey often has interesting insights that aren't mentioned elsewhere on the Internet. For example, they go over literary elements (like setting, conflict, and mood), compare and contrast, and symbolism/motifs. It's a good site if you want to find a unique fact or angle that other students don't know about.
If you're bored by traditional book notes, try Shmoop! They write their summaries in an approachable, entertaining style. Their comprehensive offering includes chapter by chapter summaries, themes, quotes, character analysis, study quizzes, and even flash cards and infographics.