Would I like this game? I mean I'm a type of gamer who likes a challenge, especially in RPGs. I've heard good things about Nocturne so I was wondering if I should pick it up from Amazon for 30 bucks. Though I have a couple of questions before buying it.
 
Is the soundtrack done by Shoji Meguro? Is there voice acting or is it unlike the persona series? 
 
 I really want to get into the Shin Megami Tensei series and Persona was fun and all, but I want see how great this game is. 

I don't know, it's a VERY different game. It's a lot more of a traditional RPG with towns and a world map, but it's also a hell of a lot harder. There's far more enemies with instant-kill spells and towards the end of the game the random deaths can get extremely frustrating. Gameplay wise it's not too far off, although instead of getting a set party like in Persona games you have to recruit enemies to fight with you, which actually makes the fusion system a lot more relevant since it applies to everyone in your party instead of just the main character like in P4. Also I'm not sure who composed the soundtrack.
 
In my opinion it's not as good as the Persona games, but if you feel like taking a risk and can handle a very serious and at times cheap difficulty level, then by all means go for it. There's a lot worse RPGs out there.

The soundtrack is done by Shoji Meguro, so it's quality stuff. There is no voice acting seeing as this came out a tad early in the PS2s life span if I remember correctly. 
 
Thematically speaking, it is a much darker game than the recent Personas.  The Social Link aspect in the recent Personas is not here either, so the only other way to boost your party (aside from grinding) is through fusion.  It makes it a much more straight laced JRPG without the S. Link distraction.  It is also a much harder game and is quite unforgiving compared to the Persona games.  
  
That being said, Nocturne is my 2nd favorite ShinMegaTen RPG with the first being Persona 3.   The story is great, and it has that old-school JRPG difficulty that you don't see anymore. 
 
EDIT: oh and it also has a lot more replayability since there are like 6 endings to the game.

Well, it's not quite as story driven as P3 and 4. It's the presentation and the atmosphere that make it worth playing. As for difficulty, I encountered no problems on the normal setting. Only had to grind once. There's a lot of random battles too.