The Great God Pan
What is now the first chapter of the novella was published in 1890 in a magazine called "The Whirlwind", while what is now the third chapter of the book was published in the same magazine the following year as a standalone short story called "The City of Resurrections". Machen only viewed the two works as connected after they were finished. Once he decided the two stories were connected, Machen wrote the rest of "The Great God Pan" in a single evening save for its final chapter. Machen did not think of an ending for the tale for months, and in that time believed that the novella would remain unfinished forever. The last chapter was completed in June 1891. Machen sent the novella to the publisher Blackwood, who rejected it, deeming it a clever story that "shrink[s]...from the central idea." It was accepted by John Lane and published in 1894. When published as a book, "The Great God Pan" was accompanied by another Machen tale called "The Inmost Light" which also features a mad scientist and elements of science fiction. The book's cover was illustrated by Aubrey Beardsley.
God Speaks
"God Speaks" has had three editions. The first edition, published by Dodd, Mead and Company, received four printings, 1955, 1967, 1968, and 1970, and was 255 pages. As early as 1956 Meher Baba began work on a second edition, which was printed posthumously in 1973 and 1975. It was 334 pages. In 1990 the original publisher, Dodd, Mead, went out of business and the plates for the second edition were not preserved. For this reason, the book was retypeset in 1997 and is 313 pages in its current form. Labeled within as the "second edition third printing" the 1997 printing is technically a third edition since it is retypeset, although no major editorial changes were made to the text. The third edition received a second printing in 2010.
There is also an Indian printing edition, published by Meher Mownavani Publishing, India, 2001.