Much has happened in the years since the publication of the seventeenth edition of The …
1.5 Book pages. The trimmed sheets of paper in a printed-and-bound book are traditionally referred to as leaves. A page is one side of a leaf. The front of the leaf, the side that lies to the right in an open book, is called the recto. The back of the leaf, the side that lies to the left when the leaf is turned, is the verso. Rectos are always odd numbered, versos are always even numbered.
— The Chicago Manual of Style by University of Chicago Press (Page 6)
Now I know where Verso Books took its name, from the left side of an open book.