Title pages of the 1917 UK and US eds. both display the title on two lines, with a slight size difference (centered, quote):
GOD
THE INVISIBLE KING
Apparently the Preface text is identical, and as below, in the 1917 UK and US editions, as pp. v-xvii and pp. ix-xx respectively.
(both viewed at HathiTrust)
Canadian publisher advertisement The Globe (Toronto) 1917-05-26 p9 fashions the title:
God, the Invisible King
(so punctuated and capitalized) and states:
CANADA IS FIGHTING FOR THIS GOD
(as Now ready at all bookstores; $1.25; Published by the Macmillans, Toronto).
1st ed.
Publication date represents 1st printing
Publisher advertisement The Observer 1917-07-01 p4 specifies 4th printing, also 6/-
Publ date from notice at the foot of publisher advertisement Manchester Guardian 1917-04-27 p3: "The new volume ... ready on 10th May."
The same newspaper -05-18 notes a review by J.C. Squire "in this week's Land & Water".
The Scotsman -05-21 p4 notes that "God the Invisible King" is reviewed on p. 2 --not available to this contributor 2017-10-30.
Price from publisher advert ("The House of Cassell, E.C.4") The Observer -05-06 p4, this one as "God the Invisible King" and "[Ready May 10]"
HathiTrust Digital Library provides full view of two copies, one from U California with original cover apparently
-- title page
-- Preface, p.v-xvii
-- Contents, p[xix], lists 8 chapters
-- text spans p1-[206]; footer "Printed by Cassell & Company, Limited, La Belle Sauvage, London, E.C. 4" over "F90.417"
The title is fashioned "God the Invisible King", on one line and so capitalized, at the top of page 1, which also shows the two-line heading of chapter 1 and the beginning of the text.