I think he is for real, however because he plays on a bad team his numbers are all a bit "amplified" if you will. Because there aren't really any good rebounders on his team besides him, het gets more boards for example. And because someone has to score, he scores and takes more shots than he probably should. The scoring is especially evidence of this. The guy can score but to have him put up 40 points is pretty crazy and has a lot to do with Minnesota as a team. But hey, he did it and you can't take that away from him.
Now all that being said, he is one of the best rebounders in the league. If you watch him board he does it in an extremely smart and practiced way. As soon as a shot goes up, he looks at the angle of the shot and you can see him dart right to a practiced spot, get low to secure the space, and get his hands ready to snatch up the board. Also notice he often doesn't even really jump off the ground to get the boards. It's all positioning. It's very impressive.
And his three point shooting has become legit this year. On the break and in the half court he has become a good spot up three shooter.
So if you put him on a better team his numbers go down. However, he is still the teams best rebounder (in all but a few cases) and a good all around player that is a good passer, moves well, sets solid screens, etc. Needs to work on his D but he is a great player, I know I'd love to have him in the Celtics green one day.