From the Kickstarter description:
We All Hate Your F#*cking Friend is a fast paced and irreverent card game, that really brings out the very best in worst behavior.
Let's say that you meet with a regular game group, and that group has lost a player. You need to fill the empty seat. All the regulars bring an imaginary friend with them, and your only job is to keep your friend from making a fool of him or herself, alienating the host's spouse, and other various acts that would get them sent packing.
We All Hate Your F#*cking Friend is a deck game with positive and negative cards all about what your "friend" does during the game. Play your cards smart and make your "friend" look good, or play against other players' "friends" to make them look like a tool.
Just keep your friend in his seat! The person with the most tolerable friend wins the game.