In 1823, in conjunction with friends he had made as publisher (1820–1821) of The Etonian, he started Knight's Quarterly Magazine, to which Winthrop Mackworth Praed, Derwent Coleridge and Thomas Macaulay contributed.

[1] The periodical included an 1824 review of Frankenstein in which Percy Bysshe Shelley was attributed as the author in a comparison with his wife's second novel Valperga.

[3] In 1827 Knight was forced to give up publishing, and became the superintendent of the publications of the Society for the Diffusion of Useful Knowledge, for which he projected and edited The British Almanack and Companion, begun in 1828.

Many famous books, Harriet Martineau's Tales, Anna Brownell Jameson's Early Italian Painters and G. H. Lewes's Biographical History of Philosophy, appeared for the first time in this series.

[8][11] In 1838 Knight took out a patent for, "improvements in the process and in the apparatus used in the production of coloured impressions on paper, vellum, parchment and pasteboard by surface printing.