What is the longest book written by J.R.R. Tolkien?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q892', 'id': 0, 'label': 'J. R. R. Tolkien'}, {'type': 'INTERNAL', 'name_': 'Q332581', 'id': 1, 'label': 'The Return of the King'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q131074', 'id': 2, 'label': 'The Lord of the Rings: The Return of the King'}], 'links': [{'name_': 'P50', 'source': 1, 'target': 0, 'label': 'author'}, {'name_': 'P4969', 'source': 1, 'target': 2, 'label': 'derivative work'}]}