There are thousands of articles and websites on Kelly on the internet. But this simple statement is worth reading:
Section 5: The Dangers of Over-Betting and Over-Estimating Your Edge
These graphs [There aren’t any! –D.S.] illustrate the long term power of using Kelly sizing to increase one’s bankroll over time, and beg the question, ‘if Kelly betting will lead to such incredible returns, then betting double or triple Kelly must lead to even higher returns!’ Referred to as ‘over betting,’ this misguided notion is one of the reasons that so many +EV sports bettors go broke just like their square compatriots. It turns out that someone betting 1.5 Kelly has the same expected growth as someone betting 0.5 Kelly, but with tremendously wilder upswings and downswings, and much more risk. Betting 2 Kelly actually has the same expected return as not betting at all: exactly zero, and betting more than two Kelly has a negative long term expected growth even if you are making positive expected value bets, and your bankroll will eventually fall to zero! In conclusion, Kelly sizing is in fact, as has been stated several times, the point at which return is exactly optimal.