Sestero seems like a pretty cool guy there! The Disaster Artist
is a fantastic read. Don't know how much of the voice is Sestero and how much is Bissell, but it's really witty; Wiseau is also a little sad and scary.
Yeah, he actually is a very cool guy. And, you are correct - the book is fantastic! (and, this is coming from a guy who has not actually read a book since school).
As far as whose voice it was written in, here's the info that I gathered in my conversations - basically, Sestero kept a journal during the making of the film, so they had that info to fall back on. Then, he interviewed his fellow cast members. Then, Bissell interviewed Sestero and watched all of the behind the scenes footage from the movie. The two of them plotted out the entirety of the book from there, chapter by chapter, and Bissell took the outline and turned it into actual compositional text. Then, the two passed it back and forth between each other to do some rewrites. So, I suppose you'd say that, it's mostly written in Bissell's voice, using Sestero's first hand accounts. But, again from my experiences, I'd say the wittiness came from both parties pretty equally. Hope that sorta makes sense!