From Nazraeli Press website:
Our popular One Picture Book series was conceived in 1998 as a way to make original artwork affordable. The series consists of uniformly designed, modestly-sized hardcover books, comprising 16 pages that serve as a “canvas” for the artist to display one cohesive body of work. 
Each One Picture Book is published in an edition of 500 numbered copies, and each contains an original tipped-in photograph, signed on the verso by the artist; hence the name of the series.