Every twenty-something needs a little black book of secrets. Our twenties are filled with confusion, terrible jobs, anticipation, disappointment, cubicles, break-ups, transition, quarter-life crisis, loneliness, post-college what the heck, moderate success sandwiched between complete failure. We need a worn and weathered guide stashed somewhere close by to help shed some light on this defining decade.

That guide is this book.

Expanded from the blog post "21 Secrets for Your 20s" that spread like Internet wildfire with nearly a million readers in 190 countries,...