From the 1915 and 1920 title pages (viewed at HathiTrust), the very long original title and credits conclude thus:
Prepared for Publication by Reginald Bliss author of [... five lines]
with An Ambiguous Introduction by H. G. Wells
and are augmented in the Second Edition thus:
Prepared for Publication by Reginald Bliss author of [... five lines]
with An Ambiguous Introduction by H. G. Wells (Who is in Truth the Author of the entire Book)
- 1st edition
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Publication date from listing as "Illustrated. 6s." by the publisher, The Spectator 1915-04-24 p562, this one annotated "[May 3."
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Price from the review "A Questionable Boon", The Academy #2246 (1915-05-22) p330.
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HathiTrust Digital Library provides full view of one copy with original front/back covers:
-- front cover minimal gold line illustration on dark cloth, no lettering (that on the spine evidently)
-- title page (first four components):
Boon, The Mind of the Race, The Wild Asses of the Devil, and the Last Trump
Being a First Selection from the Literary Remains of George Boon, Appropriate to the Times
Prepared for publication by Reginald Bliss [Author of ...]
With an Ambiguous Introduction by H. G. Wells
-- half-title page shows first component only
-- copyright page: "First published in 1915"
-- Introduction, p5-6, closes "H. G. WELLS"
-- text spans p9-342
-- no back pages, except p[343] identification of printer "The Gresham Press // Unwin Brothers, Limited // Woking and London"
There is no frontispiece. The earliest illustration, paging from the front, is a small line drawing on page 34, in the style of the front cover drawing.
The illustrator must be Wells, as Reginald Bliss.