Question: Which successful WB Television Network series includes a horror trilogy published as a book in 2001?
{'answer': 'Buffy the Vampire Slayer', 'supporting_facts': [['Unseen (Buffy/Angel novel)', 0], ['Unseen (Buffy/Angel novel)', 1], ['Buffy the Vampire Slayer', 0], ['Buffy the Vampire Slayer', 1]]}