Political theory is one of those categories of books where the precise language is very important. On the one hand, there is a temptation to read such a book in its original language (and indeed, I have Il Principe in Italian) but on the other hand, the risk of mistranslation is high. Words, even within a language, change meanings over time, so a word that meant one thing in Machiavelli's time may have a different contemporary meaning (cf. how words like "passion" have changed meanings). In addition to potential confusion caused by such changes, there are words that seem to be close to almost identical words in English that a reader may not be careful enough to realize mean something else in Italian. Ultimately, I think I would only want to read Machiavelli in a dual-language edition that allows for a good critical apparatus to track ideas and parallels (sort of like the Bollingen series for Dante, which I am going to tackle one of these days).