The first appearance of WHEN THE WORLD SHOOK was as a serialized novel, published in The Quiver from November 1918 through April 1919. A.C. Michael created 26 illustrations for the serialization.
McKay, Scott, and Whatmore claim that Cassell and Company 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 the complete serialization of this novel in CASSELL'S MAGAZINE, 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