I loved the first game and have been meaning to buy this one, but I'm wondering how long the single player is and if the multiplayer is any good?

The multiplayer is shit and especially at this point since the only people who are still playing it are the really hardcore folks.
 
I really enjoyed the single player though, I'd say it was equally as long as Bioshock, but I take my time in these games just exploring Rapture.

 
The single player felt longer than the first one, but its a great experience and worth buying. 
 IMA TRY NOT TO SPOIL ANYTHING NOW!!!!
Things i hated: 
 1. How much fucking DAMAGE YOU TAKE! I have to look for medpacs and hack every health station after every battle. 
2. The plot. Okay, the plot was okay, but Ryan was pure awesomeness. And if Ryan was still alive, i would love for him to beat the shit out of Lamb. 
3. That everything takes ammo. Sure,to be realistic, but even the fucking DRILL TAKES FUEL! 
4. NO NEW PLASMIDS! Nope, no new plasmids from what i know. It just sucks! Expect Hypnotize all foes, instead of only Big Daddies.
 
Things i liked: 
1. The hacking. The hacking from the first game sucked gigantic ass, mostly because it was super hard, but now they fixed that and im glad! 
2. The awwwwwesome characters! New enemies such as the Brute Splicer and Big Sisters are epic, that makes the game just more enjoyable. 
3. The tonics. They have included way more new awesome tonics that i very much enjoy! 
4. The weapons. New weapons for example Machine gun, which looks different from the first game. In the first it was a Tommy Gun, but in this its a minigun! 
5. The drill. Do i have to explain? 
 
PLAY THIS GAME!