The page edges?

Is it a HarperCollins US publication? Many US items have one or more edges untrimmed.

Quarto or octavo depends on how many folds per sheet to make pages: 2 folds for quarto to make 4 pages and 4 folds for octavo to make 8. Each one makes up a little section, then all the sections are bound together.

. ------------------------------------------------------------------------------------------------------------------------------------------------------Whomever you may murder, there's no police like Holmes.
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