The eighteenth-century commodifications of childhood and the sciences overlapped in the production of science books for children. This article examines a children's book written by two members of the Unitarian circle around Warrington Academy in the 1790s, and contrasts it with a Church of England work. The analysis reveals the extent to which religious differences could affect parental attitudes to the natural world, reason, the uses of the sciences, and the appropriate way to read and discuss books. Although the sciences were admitted as suitable for children, the issues of the subjects to be chosen, the purposes they were intended for, and the pedagogical methods by which they were presented, were still contested. This article also goes beyond the usual studies of children's books by focusing on non-fiction, and by emphasizing readers and use, rather than authors or publishers. Yet producing a history of reading based entirely on actual readers will be exceedingly difficult, so this article suggests an alternative, by combining accounts of actual readers' experiences with attitudes towards practices like orality and discussion.