IDG Books reported a 15% increase in sales to $44.7 million in the second quarter ended March 31, 1998. The gain was led by a 21% increase in the company's franchise group that includes the For Dummies series and Cliffs Notes, bought in late 1998. Sales in the IDGB technology group rose 5% in the quarter, and company net income increased 5% to $4.5 million. For the first half of fiscal 1999, net income rose 11.5% to $5.7 million, on a 14% gain in revenues to $82 million.