BOSTON--(BUSINESS WIRE)--Global learning company Houghton Mifflin Harcourt (“HMH” or the “Company”) (NASDAQ: HMHC) today announced its financial results for the second quarter ended June 30, 2015. Second Quarter 2015 Highlights: HMH captured 41% market share for the first half of the year in its addressable domestic education market for K-12 instructional materials. In line with its capital allocation strategy, under the Company’s share repurchase program, HMH repurchased $191 million of its co