I've just analyzed my first two months in simulator and here is my equity curve before reading Trading in the Zone:
Winning Trade Percentage: 40%
...and after reading Trading in the Zone:
Winning Trade Percentage: 55%
More importantly, my average win amount vs. average loss amount has doubled. It used to be $0.80 won for every $1 lost; now the ratio is $1.5:$1. The book has really instilled the confidence required to (1) pursue good setups without hesitation, and (2) get out with small losses.
I still have a long way to go before I am consistently profitable in a live account, but it's great to see that Trading in the Zone has made a measurable, quantitative impact on my paper trading results. Can't recommend this book enough!