Houghton Mifflin Harcourt, the publishing company headed by Irishman Barry O'Callaghan, says it has completed a financial restructuring package which includes a $650m injection of capital.

The company said this would strengthen HMH's balance sheet, cut its debt by around 60% and its annual interest costs by more than 75%.

As part of the deal, lenders and new investors will take equity in the company. Some Irish shareholders have lost all of their investments in the company as a result of the restructuring.