Is just 10,000 hours enough, or does it have to be 10,000 hours of "serious" poker playing?
I disagree with that statement as written. It would have to be qualified. A quick and dirty example is the poker de-generate who just likes to splash around in pots and have fun gambling, not really ever bothering to apply mental focus and learning advanced concepts. (there are people that call themselves pro's that fit this definition) A person like this could spend 10,000 hours at the table and not even come close to being a bona-fide expert. Concersely, a studious individual with a deep desire and some raw talent, can quickly become an expert. If he/she spends a mixture of time studying and practicing, and has the mental ability to transfer the lessons learned into applicable game tactics/strategies.
So my point I guess it is depends a little on your natural abilities, your desire to become a true expert, and what you actually spent that 10,000 hours doing.
Regardless, I highly recommend these books.
Can't argue with that one.