NPR has a great article on the posthumous publication of Shel Silverstein's book, Every Thing On It, titled: Shel Silverstein's Poems Live On In "Every Thing."
From the article:
Every Thing On It includes 145 poems in all. Silverstein eliminated many of them from his earlier books, not because he didn't like them, but because they just didn't happen to fit in the perfect order he was looking for in a given collection. Toni Markiet, editor of the new collection, worked on other projects alongside Silverstein. Markiet says the poet paid close attention to every last detail.
"He would move a piece of art over an 18th of an inch ... and look at how it looked on a page," she tells NPR's David Greene. " ... It's a slight adjustment, but to him, it mattered. I think one of the reasons his books are still so immensely popular after almost 50 years is that every tiny detail was considered."