It's not hyperbole. FFXIII-2 is an extremely well done time traveling RPG that handles multiple timelines and alternate outcomes really well. Playing through 13 isn't necessary, you can get the gist of the storyline via wikipedia or youtube, and you're good to go. The story really doesn't connect with FFXIII TOO much, but you'll want to understand who certain people are. Hope plays a big role here for instance, but strangely enough Lightning is barely in it.
Things I liked about it:
*FFXIII took about 20 hours to get going. this one drops you immediately into the action without a lot of tutorials and handholding.
*Noel and Serah are your two mains, and you have the ability to customize their fighting style (based on the "roles" seen in FFXIII) to your liking. There's weapon customization here also, and it's not hilariously broken like it was in the previous game. Weapons are easily obtainable and easily upgraded. Someone else mentioned Noel is the best hero since Zidane- I don't really agree, but Noel and Serah are pretty likable and don't grate on me to the extent that FFXIII's cast did (sans Sazh, who was awesome.)
*Your third party member is a monster character i.e. pokemon, and these all have different fighting styles. They can be switched out mid-combat as well with a couple of other ones, so your potential party is pretty large. Monsters can also be fused and cannibalized into other monsters to mix and match abilities. I didn't think I'd like the monster characters as much as i did. There's also the option to have returning characters from FFXIII in the third slot, if you're feeling nostalgic.
*It's extremely nonlinear. Its packed full of sidequests that require timehopping between timelines and locales to solve, and there are a TON of puzzles of a fairly wide variety. One that I'm particularly fond of has you manipulating the weather on a certain stage, changing the layout and enemies in the process. There's also a couple of quiz games (one is well hidden) that I thought were pretty fun.
*There's a monster arena that's full of hard ass optional bosses- some are party members from FFXIII that join you when you beat them, some are callbacks to bosses from previous FF games. Gilgamesh, Ultros, and Omega Weapon can be fought here, and will join you as a third party member if you can beat them.
*much like chrono trigger, postgame allows you to go back and beat bosses you couldn't beat the first time around, leading to "paradox endings" that change the outcome of the game. unlike chrono trigger, there's no need to play through the entire game again to see these, you can simply select an era, "rewind" time to undo your actions that took place, and play through it again as if no one has met you yet. Pretty clever.
Things I didn't like:
*The storyline is typical jrpg silliness, nothing special here. The standard tropes are in full force.
*It's not as hard as the previous game. you can probably cruise through it without too much difficulty, optional bosses aside. Of course, picking a weaker third party member ups the difficulty.
*DLC! there's a lot of it, most of which are costumes and whatnot, but the arena bosses are sadly part of this too. I'm not a fan, but again none of it is necessary to get the most out of the game. it's all bonus.
It can be had for 20 bucks new or less these days, there's literally no reason not to pick it up if you're a fan. Just about every single complaint with FFXIII was addressed here and done well.