Sir John Herschel, a friend of Atkins and Children, invented the cyanotype photographic process in 1842. Within a year, Atkins applied the process to algae (specifically, seaweed) by making cyanotype photograms that were contact printed "by placing the unmounted dried-algae original directly on the cyanotype paper".
Detail of title page of Photographs of British Algae: Cyanotype Impressions
Atkins self-published her photograms in the first installment of Photographs of British Algae: Cyanotype Impressions in October 1843. She planned to provide illustrations to William Harvey’s Manual of British Algae which had been published in 1841. Although privately published, with a limited number of copies, and with handwritten text, Photographs of British Algae: Cyanotype Impressions is considered the first book illustrated with photographic images.
Eight months later, in June 1844, the first fascicle of William Henry Fox Talbot's The Pencil of Nature was released; that book was the "first photographically illustrated book to be commercially published" or "the first commercially published book illustrated with photographs".