Too Big to Fail: The Inside Story of How Wall Street and Washington Fought to Save the Financial System from Crisis — and Themselves

by Andrew Ross Sorkin

Here was an obvious red flag, for Buffett had a simple rule: He couldn’t invest in a firm about which he had so many questions, even if there were purported answers.

If you can't understand it, that doesn't mean you're dumb, it means it's more complicated then it needs to be.