Future diary is hunger games with diaries that tell you the future. When there's only one survivor left... then that survivor becomes god of the world with special powers. Of course, that description doesn't really explain how great this anime is.
The main character is retarded. But it's okay because although he's the main character, the story is all about Yuno. Not Yukki. Yukki is the main character. He's a middle school boy who is totally useless. He has no friends and all he does is record his days into his journal. His surroundings get recorded into his journal every 10 minutes.
He imagines a god and talks to god in his imaginary world. God gives him a phone that has his diary entries all filled out. He thinks he's on top of the world since he can predict the future and avoid the bullies. Life is good. Until people start trying to kill him.
Gasai Yuno is what I consider to be the main character / character that defines the show. She is amazing. She is the pinnacle of the crazy stalker girl in all anime shows. She carries the show. You should watch this show just so you understand one of the main anime characters of our time. I think Gasai Yuno will go down in anime history as one of the greatest characters ever created and become as well known as Sailor Moon or what not.
So Gasai Yuno is Yukki's stalker. Her diary records what Yukki does in 10 minute intervals. Oh right, I should probably go back and write about the diary's special powers. So there are a total of 12 characters with future diaries. The diaries all existed prior to them becoming future*ized. So Yuno's diary was already recording Yukki at 10 minute intervals. And other people's diaries also already existed before gaining the ability to predict the future. Each of the 12 characters have a unique diary and a unique prediction power based on what type of activities they were previously recording.
Yukki's diary is useless for him since it can't protect him since he never writes about himself. But Yukki with Yuno's diary is an amazing tool because then Yukki knows pretty much everything that will happen to him. The anime is basically a series of conflicts between diary owners trying to find each other and kill each other. Yuno is just such an amazing character. The thing I didn't really like about this anime was how useless Yukki was. I guess you needed Yukki to be useless in order for Yuno to shine. And plus, it's all about feminism these days and role reversal. So it's cool to have a totally useless male protagonist.
One note of warning is that the anime is quite dark. I actually really enjoyed one of the piano themes in the OST. Overall I'd say Future Diary is quick good in the suspense/thriller/mystery genre. It's not as good as Steins;Gate but it I really enjoyed it from start to finish. At some point as I was watching it... I just got the marathon urge where I *needed* to know what happens at the end. I pretty much marathon'd the last 10 episodes cause it's like... the mystery build up.
Scoring: Enjoyable and recommended. Watch it.