Macmillan is expanding their program to “test subscription” services for ebooks. After starting with 1,000 titles available through both Scribd and Oyster in January, the publisher is adding “more than 1,000 additional titles” to both services, along with more than 300 children’s titles. While it moves Macmillan forward with both subscription operators, it still leaves them shy of the participation levels from HarperCollins (which offers substantial backlist, and had put the 15,000-title Harlequin backlist in before Scribd recently cut their romance title selection) and Simon & Schuster, which offers its entire backlist for subscription reading.