I have friends who read The Prince like a bible, and its true that Machiavelli is worthy of repeated study, both as a period piece and window into the Renaissance Italian soul, and as possibly the most notorious treatise on Realpolitik ever written. Machiavelli, like Nietzsche, has been misused by the unscrupulous and decried by the ignorant; also, IMHO, both writers were actually better historians and analysts than they were philosophers per se.
Baltasar Gracian, in the Pocket Oracle, has accomplished what Niccolo never could, nor would have wanted to: a day to day primer of sage advice from a trained Jesuit mind who walked and worked in the highest halls of power in his time. The lessons are pithy and epigrammatic, both simple yet deserving of deep reflection and consideration and, most importantly, are eminently USEFUL in almost every interpersonal interaction in your day to day life, whether you are a dish washer or a senator -- his teachings are that universal.
Robert Greene strip-mined Gracian for 48 Laws of Power, but again IMHO, it's always best to refer back to the seminal source even after being presented with a good a digest as Greene presented. This is the Penguin edition, so you of course have the value added of their wonderful introductions, with historical references anchoring Gracian's life and the impact of the Oracle itself. Also, this translation is, I feel, much better than those I've seen marketed under the variant title Art of Worldly Wisdom.
I read this book everyday. I recommend it to every man woman or child that wants to live their very best. Gracian was one of the wisest men who ever lived, and this is the free distillation of his wisdom.