It is now widely accepted that reporting the results of randomised controlled trials should encompass a complimentary focus on both outcome measures and process measures. Reflective of the current thinking, this article reports on the findings from a qualitative evaluation that accompanied a randomised controlled trial of the Letterbox Club; a book gifting intervention for children in foster care. Outcome measures used in the trial have recently been reported on (Mooney, Winter, & Connolly, 2016). Findings showed no significant effects in terms of improvements to children’s literacy skills and/or enjoyment of reading. Through in-depth interviews with 20 foster children, their carers and the programme developer, the qualitative evaluation focused on how and why the intervention did not achieve greater impact. Findings illustrate differences between the ‘hoped for’ outcomes of the intervention, and carer/child levels of engagement with and experiences of the programme. In order to move the programme forward and begin to explore the findings, a logic model is suggested which accounts for the current findings regarding the use and lived experiences which carers had with the packs. Wider implications for the conduct of these types of randomised controlled trials are discussed.