The poor educational outcomes of children in care are a significant concern internationally. Whilst there have been many interventions developed to address this problem, very few of these have been rigorously evaluated. This article presents the findings of a randomised controlled trial that sought to measure the effectiveness of a book gifting programme (the Letterbox Club) that aims to improve literacy skills amongst children aged 7–11 years in foster care. The programme involves children receiving six parcels of books sent through the post over a six-month period. The trial, which ran between April 2013 and June 2014, involved a sample of 116 children in Northern Ireland (56 randomly allocated to the intervention group and 60 to a waiting list control group). Outcome measures focused on reading skills (reading accuracy, comprehension and rate) and attitudes to reading and school. The trial found no evidence that the book-gifting programme had any effect on any of the outcomes measured. Drawing upon some of the emergent themes from the accompanying qualitative process evaluation that sought to determine foster carer/child attitude towards and engagement with the parcels, it is suggested that one plausible reason for the ineffectiveness of the Letterbox Club, as intimated by carers and children (rather than explicitly explored with them), is the lack of support provided to the carers/children in relation to the packs received. Reflective of an ecological model of children's development, it is recommended that for book-gifting programmes to be effective they need to include a focus on encouraging the direct involvement of foster carers in shared literacy activities with the children using the books that are gifted.