Previous research shows that children from socioeconomically advantaged families read more than children from less advantaged homes. This article studies how inequality in the amount that children read accumulates across childhood and the extent to which this inequality depends on the cultural inputs parents provide. Additionally, the article studies whether children’s or parents’ cognitive ability moderates the effect of cultural inputs. Based on a Dynamic Panel Data Model and data from the National Longitudinal Survey of Youth 1979—Children and Young Adults Supplement, I find that the amount that children read depends on both the cultural inputs they currently receive, but also on those inputs received in previous years (which shaped how much they read in previous years). This cross-time accumulation, coupled with a socioeconomic gradient in the levels of cultural inputs parents provide, leads to growing inequality in children’s reading. I do not find that cultural inputs are more effective in encouraging children with higher ability or children of mothers with higher ability to read more.