No title
At first, I was very disappointed at the game not having any voice acting, but Mirai Nikki is a thoroughly enjoyable experience and the lack of voices is the only reason I'm giving it 4 stars instead of 5.
First and foremost, if you plan on buying this, you must realize that the game is basically a visual novel and therefore your Japanese must be quite good. Also, the story might be confusing for someone not familiar with the original manga.
The game sports a slick interface with beautiful character and background art. The scenarios flow well, and the music sufficiently contributes to building the mood. Several innovations make this game stand out, such as the Yandere Operation system, which entails Yuno eliminating some of your choices when her bar is full (sometimes for better, sometimes for worse). You can also look at your diary at practically any point in the game, though this is done automatically when the entry affects the story.
I should warn you that the game is pretty difficult. It is easy to die when you make the wrong choices, so you might find yourself playing through a particular scenario multiple times before getting it right. On the other hand, there is a convenient SKIP function that only skips text you haven't read before, and similarly choices you have made before are distinguished from new choices by colour.
I haven't finished the game yet, but between the exciting story and the many unlockable extras, I can see myself enjoying this game for a long time still.
日本版 
