Bruce Berkowitz is at it again.

Best known for making aggressive investments in retailers such as Sears Holdings (Nasdaq: SHLD) -- where he's the No. 2 biggest stakeholder after Eddie Lampert -- and real estate developer St. Joe (NYSE: JOE) -- where he's the No. 1 biggest shareholder -- the founder of Fairholme Capital made headlines once more this week, when he made some big moves in the banking industry.

According to StreetInsider.com, Berkowitz sidestepped this week's European blowup by selling out early (and often) on his investments in Goldman Sachs (NYSE: GS) and Morgan Stanley (NYSE: MS). Liquidating both positions, Fairholme continued the selling spree as he shed shares of Citigroup (NYSE: C) and Regions Financial (NYSE: RF) as well.

But it's not all doom and gloom. At the same time that Fairholme fled many of the nation's biggest bankers, Berkowitz apparently doubled down on investments made earlier this year -- in Bank of America (NYSE: BAC). At last report, SEC filings show Fairholme holding 81.9 million shares of B of A.

Why? Berkowitz isn't saying, but if you read between the lines, the answer's clear:

Bank

Price-to-Book

Forward P/E

B of A 0.3 6.6
Citi 0.5 6.6
Regions 0.3 7.8
Morgan Stanley 0.5 7.8
Goldman 0.8 7.7

Source: Yahoo! Finance.

Not to put too fine a point on it, but while many banks look cheap these days, none's quite as cheap as B of A. It's tied for price-to-book with Regions, and it ties with Citi on forward P/E.

As we saw in the past two days' sell-offs, investing in big banking remains a perilous business. Three years after the Great Recession began, still no one's quite sure "what's inside the box." Meanwhile, the least little whisper of trouble in Europe can still set off a panic. It makes sense, therefore, to limit your exposure...and widen your margin of safety.

Moral of the story: Bank of America may not be the best stock in banking, but it's darn near the cheapest. That's what Berkowitz sees in it. That's why he's buying.

Or so say I. But do you see another reason Fairholme Capital might be enthused over Bank of America? Tell us about it on Motley Fool CAPS. While you're at it, add B of A to your Fool Watchlist -- if there's more to this story, we'll tell you about it as it happens.