The earliest appearance of WHEN THE WORLD SHOOK that I know of is as a serialized novel, published under the title YVA in America in The Pittsburgh Sunday Post Feature Section of The Pittsburgh Post. While I do not own and have not seen the first part, I do have what is likely the second part, dated February 24, 1918. The San Francisco Examiner began its serialization of this novel on February 24, 1918 (The American Weekly section). Howard Chandler Christy created the color illustration of the first part that appeared in The American Weekly. And, it seems that Edmund Frederick created the rest, an unknown number, of the illustrations for these serializations.
The earliest appearance of WHEN THE WORLD SHOOK in Britain is as a serialized novel, published in The Quiver from November 1918 through April 1919. A.C. Michael created 26 illustrations for the serialization.
Higgins claims that Cassell and Company paid £400 ($39,000 in 2020 dollars) for the serial rights, and £750 ($73,000 in 2020 dollars) was advanced for publication in book-form.
McKay, Scott, and Whatmore claim that Cassell published the first edition in book-form in London on March 20, 1919. None of Michael's 26 illustrations are in this edition, though there are 2 plates in black and white of 4 charts of stars. There are no ads at the end of the book. McKay and Scott claim that 14,000 copies were printed. The last page has a date-code of 219 (February 1919).
Longmans, Green and Company published the first American edition May 22, 1919. McKay and Scott both agree on the publication date in New York. In addition to a full-color frontispiece by Enos B. Comstock, the American edition used the same star-chart illustrations as Cassell did for its edition. There are no ads at the end of the book.
See the VisualHaggard.org page dedicated to the illustrations found in various editions.
I own three different parts of the YVA serialization from three different newspapers
I own the complete serialization of this novel in THE QUIVER, and below is the front cover of the first issue, which is in my collection.
Below: A few of A.C. Michael's illustrations, including this large one covering 2 pages
I do not own and could not find any images of the Cassell British first edition original dust jacket
A facsimile DJ is shown below for illustrative purposes
Below: Copies of the British first edition, variant bindings, none in my collection
Below: the British first edition title-page
Date-code of 219 (February 1919) on the last page
Below: A copy of the British first edition signed for Mrs. Pitt that I saw on the Internet (not mine)
Below: A nearly perfect Longmans, Green American first edition with original dust jacket, sadly not in my collection
Below: A copy of the American first edition original dust jacket that I wish I had not sold to someone else
My copy of the American first edition
I also own a copy of the 2nd printing