Children who read regularly with their parents or carers tend to learn language faster, enter school with a larger vocabulary of words and become more successful readers in school. Because of this, local authorities often commission services to promote family-based shared book reading. However, recent studies suggest that shared reading interventions work less effectively for children from disadvantaged backgrounds than originally thought, particularly when their parents have lower levels of education. This means that there is a danger that the benefits of shared reading will be restricted to children from more affluent homes and not get through to those who need them most. To solve this problem, there is a need to develop a better understanding of how reading interventions work and to evaluate existing shared reading interventions to determine whether they are effective in promoting young children's language development.