Leggett suggests a catastrophic an oil shock within 2 years, only possibly delayed for a few years by another financial crisis. He does not suggest this lightly. From his first-hand accounts, it is a view shared by other credible sources: in the International Energy Agency, in city boardrooms and within the US military.
His early peak oil view, which he thinks has been swept under the carpet by the 2008 financial crisis, apparently lurks right around the corner in 2015. Leggett uses this book to update views already laid out in the books The Carbon War and Half Gone. Nevertheless it is fresh and very readable.
He may be wrong to underplay economic adaptive solutions. And suggesting that the climate crisis might be solved during economic upheaval is also tennuous. But the evidence is well laid out and anyone engaged in aspects of the global energy challenge should do more than take note.