Sometimes, a sprawling historical novel is a perfect ticket to a pleasant escape. A gripping story, engaging characters and descriptions of other times and other places can entertain and educate. And that’s just what Julia Gregson serves up in “East of the Sun.“ As the story begins in London in 1928, 20-something Viva Holloway, a penniless orphan and an aspiring writer, has been hired to chaperone three younger people on their voyage to India. Viva has received word from a woman in Simla that a trunk belonging to Viva’s late parents has been found, and that’s all Viva needs to flee her humdrum life in England, a place she has never felt at home. Both her parents and her sister died in India, and the subcontinent calls to her.