A few comments:
Returns
You can’t compare the returns given in the book and reach the conclusion, as Zuckerman does, “that no one in the investment world comes close [to Medallion].” The returns for the funds listed in the appendix are internal rates of return (and effectively the compounded annual growth rate for Berkshire). But Medallion’s is an arithmetic return. For a fund like Medallion that pays out most of its earnings (they’ve distributed 10x their current capital), the arithmetic return will be very different from the compounded return. Consider that if Simons was indeed able to compound at 66%, the initial $18 million in Medallion would now be worth $120 trillion ($18 million*1.66^31 = $120 trillion).
I would actually prefer to have an investment return, say, 15% and reinvest at 15% over one that returned 66% but couldn’t reinvest. It wouldn’t even be a close call.
Leverage
Renaissance isn’t the only firm operating with a lot of leverage in the financial world. Banks are levered +10x and do fine. Same with trading houses (Marc Rich + Co, Phibro, etc.), which run +20x. Even market-makers (Citadel and all the Chicago prop shops) seem to do OK with +30x leverage. What’s even more remarkable is that they all do it with either short-term funding (commercial paper, letters of credit, repo, etc.) or call loans (margin debt, demand deposits, etc.).
I wouldn’t want to have 30:1 in call loans against soybeans or some other commodity, but a lot of people seem to make it work.
“Is value investing not the only way?”
I don’t understand what the big deal is about Renaissance. Is it really that surprising someone with a 180 IQ and a background in mathematics is making money trading? He’s not the first and he won’t be the last.