Trump is authentic. Authentically terrible, but authentic. His positions are for the most part things he's seemed to believe in for decades, and despite wolololoing all over the place on social issues his isolationist nationalism and bullheaded economic beliefs can be observed all the way back in the 90s and previous. Further, his personal style is consistent and interesting.
I suppose it depends in part on which version of Trump you mean; to some degree his mask has been fragmenting, but when he has his whole branding apparatus in place and functioning, he's the "blue-collar billionaire." The whole "he tells it like it is" schtick is just part of that attempt to seem earnest by saying things that people with his wealth generally avoid saying in public, but that they are shocking does not make them any less calculated.
In a way, Trump is like a glitzier version of Dubya: he plays the idiot knowing that people will either believe the act or believe that, by seeing through it, they're seeing through to the "real him." Conveniently, the "real him" is as canny as they believe themselves to be, instead of merely a different, sadder, more mundane kind of idiot.
Trump is neither the buffoon he pretends to be at his rallies nor the tycoon he wants you to think is putting on the act. His team allows certain of his vices to show through to lend an air of authenticity to both, but beyond the hamburgers and the affairs is just a deeply unhappy old man who was never quite as smart as his dad wanted him to be.