Sales at Penguin Random House rose 16.2%, to 1.70 billion euros, while earnings increased 30.2% in the first six months of 2015.

Parent company Bertelsmann attributed the results to a roster of bestselling novels that include The Girl on the Train, Grey, The Life-Changing Magic of Tidying Up, What Pet Should I Get and Between the World and Me.

In remarks made in Germany during the presentation of results, Bertelsmann chief executive Thomas Rabe said the company would consider upping its stake in PRH, which now stands at 53%, with Pearson, the former parent company of Penguin, owning 47%.

In his letter to employees, PRH CEO Markus Dohle said that even in his “most optimistic moments I could not have foreseen the publishing successes we have been enjoying this year.”

Outside of the U.S., Bertelsmann noted that Penguin Random House Grupo Editorial had an “excellent performance” in Latin America and double-digit growth in e-book sales. The latter offset problems in the Spanish book market. The company also made progress in integrating the Spanish and Portuguese-language publishing activities of Santillana Ediciones Generales, which was acquired last year.