His Lancashire novels cover altogether 400 years and include "The Lancashire Witches", 1848, "Mervyn Clitheroe", 1857, and "The Leaguer of Lathom". "Jack Sheppard", "Guy Fawkes", 1841, "Old St Paul's", 1841, "Windsor Castle", 1843, and "The Lancashire Witches" are regarded as his most successful novels. He was very popular in his lifetime and his novels sold in large numbers, but his reputation has not lasted well. As John William Cousin argues, he depends for his effects on striking situations and powerful descriptions, but has little humour or power of delineating character. S.T. Joshi has characterized his output as an "appalling array of dreary and unreadable historical novels". E. F. Bleiler has praised "Windsor Castle" as "the most enjoyable" of Ainsworth's novels. Bleiler also stated "All in all, Ainsworth was not a great writer--his contemporaries included men and women who did things better--but he was a clean stylist and his work can be entertaining".