John Wiley reported this morning that sales of print books plunged in the third quarter that ended January 31.

Revenue from what Wiley calls Education Books, which is primarily higher education textbooks, tumbled 27% in the period, compared to the third quarter of fiscal 2016. The drop, Wiley said, was due to the rental textbook market and “other market forces.” Sales of STM and Professional Books declined 12%.

The weakness in sales of print books offset gains in Online Test Preparation, Course Workflow, and Licensing units. Overall, revenue in the publishing group dropped 15%, to $171.4 million, compared to last year’s third quarter.

Total revenue for all of Wiley was flat in the quarter at $436 million, while net income rose to $47.4 million in the quarter from $35.5 million in last year’s third period.

For the first nine months of fiscal 2017, publishing sales were down 12.5%, to $479 million, while total company revenue fell 2.0%, to $1.26 billion, and net income dropped 39.6% from the first nine months of fiscal 2016, to $67 million.