Sorry about that, I meant CCC. I actually own the special edition of Extra for the PSP. Extella takes place in the same universe as the Extra games, but for the most part, you'll be able to enjoy this one without playing the previous two, you might miss a reference or two about the previous games, or wonder why certain servants act the way they do towards the player character, but aside from that, you'll still be able to enjoy the game. I do recommend Extra though it's pretty fun.
Main thing you should know if you're coming from the anime series is that this isn't related to them, it's very much its own thing, aside from certain servants and characters from the anime/VN that show up, and even then, those sometimes behave in completely different ways, also, it doesn't take place in the real world (or earth for that matter), rather, the whole thing is a simulation inside a magical-super-computer-of-doom that's on/is the moon.
Been a while since I played Extra but that's the most important thing I can think of right now.
TL;DR You should be fine playing this even if you haven't played the others, but Extra is a fun game!