question: How many of the Heroes of Olympus books are there?
answerText: 5
questionEntity.name: Q25211942
questionEntity.entityType: entity
questionEntity.label: Heroes of Olympus
questionEntity.mention: Heroes of Olympus
answerEntity.name: Q2356878
answerEntity.label: The Lost Hero
answerEntity.name: Q1277076
answerEntity.label: The Son of Neptune
answerEntity.name: Q3283718
answerEntity.label: The Mark of Athena
answerEntity.name: Q2274863
answerEntity.label: The House of Hades
answerEntity.name: Q17985964
answerEntity.label: The Blood of Olympus