First things first, when I say mindless fun, I do mean mindless. It's hacking, slashing and zombifying great fun, but if you're after a deep game with strategic gameplay and an excellent story, then this probably isn't the right game for you. If however you're a fan of any other hack and slash game then this game will be more gratifying.
The graphics in the game are good for a psp game, and certainly a lot better than a lot of other games on the machine. The backgrounds for the areas of the game can get a bit repetitive, though the character sprites are pretty much top notch, and even the enemies are varied enough to not get boring too quickly. The cutscenes are also pretty good throughout, which is nice for a psp game.
The sound is also a welcome change from the repetition you get in a lot of the genre, and whilst there's still a lot of grunts when attacking and being hit, the sounds really fit in with the setting of the game. There's even quite a bit of profanity peppered in characters and enemies speech, which at least livens the grunts up in some respects. The music in the game is a heavy rock genre, which fits nicely with the medieval zombie setting.
The gameplay is either where the game shines the most, or where it is most let down, depending on what you are looking for in a game. For me, the gameplay was the best part of the game- in general you go in fighting using two attack buttons, then use another button to grab your enemy and turn them into a zombie, which you can then control to do a variety of tasks- attacking enemies, knocking down structures and even making a zombie bridge. Using them to fight by throwing them into a group of enemies, or a bunch of them onto a large enemy is fun no matter how many times you do it.
Story wise, yeah, well, it's your basic out for revenge story at the beginning, but the plot twists keep the story fresh and the general idea is a pretty good one, quite interesting and the story should keep you interested enough to continue through the game.
Overall, play this game if you like hack and slash games, as at it's core that's just what this game is. Pick it up, play a level and put it down again. Incredibly fun, but not very deep.