The past three years have been a gold mine for business writers. Many books on the crisis are junk and/or marketing campaigns for a financial or political product. I haven't read them all, but two stand out from the crowd. Both are available as eBooks or in soft covers.
Tyler Cowen: "The Great Stagnation: How America Ate All the Low-Hanging Fruit"
Cowen is head of economics at George Mason University. He sees the US having run out of the beneficial extras we had before the 20th century. This process started in the 1960's to '80's. Fairly short good read. Politically neutral.
Liaquat Ahamed: "Lords of Finance:The Bankers Who Broke the World"
Biographical history of the Big Four central bank heads in the 1920's and '30's. It was largely written before 2009 which is gently ironic. This book demolishes some dogmas on Keynes, Roosevelt, and the US FED of the late '20's. It also fleshes out the contributions of J.P. Morgan before and after his grand 1907 performance, before the FED. Beautifully written. Hard to lay it down once you start reading.