This is awful, you should play it.

Man, where do I even start with this game...
Crisis Core is a prequel to the story of Final Fantasy VII in which you take the role of Zack. You know, the guy that was in the original for like 3 scenes, but was actually really important to the story? Yeah, that guy. Doesn't sound too interesting? WELL THIS GAME HAS GAMBLING AS ITS CORE MECHANIC, HOW ABOUT NOW? I will get to that later.

As far as story goes, this game is a RIDE. If you've ever had the pleasure of experiencing Deadly Premonition, this is the Final Fantasy version of that. I'm talking full on camp, cheese and awkward pauses. The amount of cheese the dialogue throws at you is astonishing, I really commend the devs on their work. We've got it all: awful voice acting, characters with a single defining trait and an anime antagonist who only speaks in verses from his favorite book. The funniest thing about this is the fact that this game is pretty essential if you want to get the full grasp on the story. Oh man, I love it.
Some might say the story and dialogue in this game is bad, I say they just don't get it. The ending is pretty damn great in all honesty.

When it comes to gameplay, it plays nothing like the original. This is a PSP game, and as we all know, all PSP games are required to have action combat. You get a default attack, a guard, a dodge and 6 spells*, but it mostly comes to using a single spell that exploits the enemy's weakness. This would get boring really quickly, but as I mentioned before, YOU ALSO GET GAMBLING BABY.
Any time you are in combat, the game will start spinning the slot machine. Depending on what it lands on, it can either grant you nothing, a small buff, or THE POWER OF GOD HIMSELF. Oh, you just wish to level up your character or your materia? Well, I hope you are good at spinning, because that is also locked behind the slot machine.
To be frank, even with this absurd mechanic, the gameplay does get stale after a while. Especially when you take into consideration that this game features a kind-of-optional-but-not-really mission system. Missions are like side-quest combat instances that will take you somewhere between 30 seconds and 20 minutes. They all reward you with something for completing it, which ranges from a consumable you will never use, to essential upgrades that you will need, especially if you want to finish this game on the Hard difficulty. There are 300 of them by the way. 300. One of the missions requires you to kill 1000 enemies. You usually fight like 3 at the same time. Yeah.
Speaking of Hard difficulty, good luck with the final boss.

2007 Square Enix was truly a different beast. This game blows, highly recommended (on a sale).

I would say mixed if we had that choice, but I do not recommend this to anyone but the most hardcore FF7 fan and even then it has its problems.

First, as a prequel, I am baffled. The pretentiousness is off the charts and like almost all post-FF6 games, is filled with implication rather than effortless storytelling. The writers wrapped the story around the in-game Loveless poem/play and it was extraordinarily confusing. I just wasn't following along and that cost me at the end where one of the antagonists says something that has serious implications to our Protagonist, Zack, and yet I understood nothing about it so I missed it because the poem/play was so vague as to mean almost nothing throughout the story. Then, there is the hamfisted inclusion of Cloud, which I could barely register as human, he was so worthless until he needed to do something superhuman. I don't think this was a good prequel, it didn't do much other than kind of explain how Cloud came to get the sword, but fleshed out a number of antagonists that seems dreadfully at odds with their FF7 counterparts. Maybe this was made in mind for the remake, which I haven't played yet.

Second, as a game, it has some of the best stuff Square-Enix has ever done, unfortunately the package they wrapped it in was terrible. 300 small side missions were a slog to go through, the later enemies are unforgiving and require meta builds to even get through. 20 larger side missions would have sufficed imo. As it is, the side content is just painful if you want to go through all of it.

Lastly, the combat carries the game pretty hard, the main character is unfortunately a lot more interesting than Cloud ever was, but more unfortunate, we never build a real relationship between the characters. Cloud is a passing acquaintance to Zack at best. This is a major missed opportunity and something that doesn't square with the ending, where Zack leaves his legacy with Cloud, despite them not really knowing each other very well. Zack helps Cloud out primarily due to his own ethos, not because they share some kind of bond other than both being country boys. It could have been so much more relevant to the plot of FF7, but it does a minimal job of setting the stage; choosing to mainly be a character study of someone who is barely relevant to the plot of FF7. And for that, I am sorely disappointed.

One of the Best PSP game era !!