Cards Against Humanity is a terrible game that you should never buy. Because chances are, you already have friends who have bought it already. So go find them, find a few other people, and get ready to groan...a lot.
There is absolutely nothing difficult with Cards Against Humanity, and it's simple to learn. Everyone draws the same amount of white answer cards, and each person takes turns drawing a black card with a question on it. Everyone but the person who asked the question must supply an answer that they believe is awesome, and it's up to the person who asked the question to randomly read the answers and select the best one. Whoever gave that answer gets the black card, signifying they got a point. And whoever reaches the set goal of points wins.
The content, however, is quite harsh. If you're easily offended, you will NOT like this game. Stop reading, go pull out Forbidden Island, and enjoy your life. If, however, you have friends who are quite liberal with their humor, this game can be somewhat good to pass the time.
Then here's what I'll say about Cards Against Humanity: it's filler. All of it. You're not going to arrange full game nights centered around Cards Against Humanity unless it involves drinking. And don't play the game with the intention of playing another, more strategic board game afterwards; this game will turn everyone into a pile of giggling mush, and no one will be able to rub two brain cells to spark a file when they're through with CAH.
So, why should you care? Because it's HILARIOUS!! It's great to play when you get a round with friends, and you'll look forward to what question comes up next.
It was Funny the First Time...
Its lasting appeal, however, is very short. After playing a lengthy game with one group, you'll find yourself seeing the same answers for typical questions, or worse - you'll have rounds where all the answers are just dull. And then there are overly-powered answers that seem to be a great fit for ANY question, making them tiresome every time someone plays it.
So, bottom line is, if your friend has the game, play it. No need to buy it for yourself because you know one of your friends has a dirtier mind than you.