Green’s Dictionary of Slang

three and sixpenny thoughtful n.

[play on penny dreadful under penny n.; shilling shocker under shilling n.]

(UK society) ‘a feminine theory novel’ (Ware), e.g. those of Mrs Craik (1826–87) or Mrs Humphry Ward (1851–1920), who wrote on social and religious themes, often dealing with women (but never suffragism).

[UK]Daily Tel. 27 May in Ware (1909) 244/2: Fielding [...] is so constantly in the bands of his countrymen of mature years, they show so marked a preference for him as a novelist over the author of the latest ‘shilling dreadful’ or ‘three and sixpenny thoughtful’, that they long to admit the younger generation to a share in their enjoyment.