I'm all for remarkable claims. If you had told me 2 years ago that not eating wheat could literally cure certain seasonal allergies, I would have thought you were crazy.
That said, I think Ferriss is very good at what he does, which is marketing.
I'm sure he approaches his training intelligently, from what I've read on his blog. But, I doubt that many people are going to be able to replicate his results consistently.
(Except for the add 150 lbs. to your lifts part -- that should be possible for any novice [and most dedicated intermediates], depending on the lift. Also, as JakeA said, I'm guessing the 2-hour sleep thing is a polyphasic sleep cycle -- which can work in the short run but is very difficult to maintain in the long run.)
I would be pleasantly surprised to be proven wrong here.
In particular, his "34 lbs. of muscle" claim seems to me outrageous, overblown, and gimmicky. He implies on the blog that he went from 146 to 180 lbs.
First of all, he used to weigh around 187-190, and was pretty well muscled. It is much, much easier to re-gain muscle quickly than it is to gain muscle quickly. If you've been 190 previously, it's not that hard to re-gain weight up to ~180.
Second, he is no stranger to cutting weight for fights, seeing as how he once cut 28 lbs. in 18 hours (or claimed to, but I have no reason to doubt him on this one). So, is it possible that Tim dehydrated himself somewhat before his first weigh-in to seem even more puny than he was? I don't mean to make an explicit accusation here, but I wouldn't put it past Ferriss, who is an expert marketer. (If he explicitly denies using tactics of this sort, I'll be happy to retract my speculation.)
Note that I have fewer problems accepting his "on 4 hours of gym time" claim. If that worked for him, great. What really irks me is that he is marketing his book on the idea that he gained an outrageous amount of muscle in a short amount of time, and that anyone else could hope to replicate his results.
I haven't read the book and have no plans to, so take all that with a grain of salt. I don't mean to dismiss any of the information in the book, but I do mean to say that the marketing strikes me as both brilliant and sketchy.
EDIT: added phrase in brackets
EDIT 2: Dec. 13, 2010: I just read his sample chapter and am definitely interested in reading the book now, so I take back what I said about having no plans to read the book. Two main reasons for my interest:
It may turn up some useful lifehacks related to fitness/wellness. Ferriss has a knack for finding them.
It may turn up some interesting anecdotes about what kinds of achievements are possible in certain individuals, which I find inspiring and motivating. In some cases, those achievements will be attainable for me, too (to some extent).
I still have a problem with selling the book as "I gained 34 lbs. on 4 hours, and YOU CAN, TOO!" I stand by my claim that it is very unlikely that will be replicated unless you are regaining previously lost muscle (and possibly do some dehydration for the "before" measurement).
EDIT 3: Dec. 14. I just read Chris Masterjohn's review of the book and am further going to eat my words. I get the impression that the content of the book is going to be better than the gimmicky marketing. (E.g., the cover implies an extreme form of polyphasic sleep, but Ferriss actually recommends a more moderate approach in the book). I guess that's what I get for trying to comment on a book I haven't actually read.