The Sparrowhawk Companion has become an indispensable reference book for readers of the Sparrowhawk series, containing, in addition to essays by the author and other contributors about the series and period in which it is set, a chronology of Acts of Parliament from 1650 onward up until the conclusion of the American Revolution, a glossary of 18th century terms encountered in the series, a handy list of the 375 characters that appear in the story, a list of all the naval and merchant vessels, and a selective bibliography of some of the author's sources. The Companion was originally published in 2007. This is an edited edition which includes a new essay by the author that was omitted from the original edition. Cline has also published two detective series, one suspense series, and, in his "War of Ideas" series, five anthologies of his political and cultural columns.