Tight and amost square (square at top, 1/8" or less tilt at bottom); spine is flat with a line down length next to cover - overall appearance is near-Fine - except for sticker-removal traces at upper right corner of front cover. This is completely re-set from other paperback editions - with larger type, more generous margins - thickness is almost double of other paperback editions (1-1/4" thick.) [I would very much like to compare this to a 1919 first edition - I suspect that is the goal aimed for in the typesetting.]

This is actually a "fix-up" - with Chapters 1 to 5 rewritten and condensed from the story of the same title in All-Story Weekly June 22, 1918. The rest of the book (Chapters 6 to 35) had origins as "Conquest of the Moon Pool" - a six part serial in All-Story Weekly, beginning February 15, 1919. (I haven't seen a copy of that original to compare the texts - so I can't say how revised the book version is...)