I just finished the TF 2 campaign an hour ago prior to the writing of this review.
Bought it on a steam sale, have been playing MP of it.
It's a ridiculously good game. Do not sleep on it. I can not make that clear enough.
And that's just the MP?

Genuinely such a top tier shooter game.

The SP is as if they took all the wacky game directors and story writers from when Valve made actual games and put them all in one room.
The campaign isn't really long, but damn is it good.
Each level is packed to the brim with incredibly creative scene changes, interesting story, a tug of the good ol' heartstrings, fun all around.
mwah. 10/10.

Btw if you're not sold by what I just said, let me just say -
I finished the campaign in like 5 hours. I am writing this review at ~40 hours.
That's how addictive the multiplayer is, I genuinely couldn't find time to finish the damn campaign itself.
You will NOT regret this.
If you feel like twitch-y fast shooters aren't your thing, at least get it on a sale for the story.