The #LetBooksBeBooks movement is about not labeling books for one gender or the other. I can think of almost countless instances where a book cover turned off a reader. The kid whose friends laughingly questioned his choice of reading because the cover was "girly"--that the content was decidedly not "girly" made little difference. I didn't see him reading that book again. This story goes the other way too, with girls not being or feeling included because of their reading choices as well. Some of the stories you'll find on the petition website are a little surprising and sad. Here's a little cover comparison to illustrate the situation for secondary readers:
While I thought these initial two covers for Beth Revis' Trilogy Across the Universe were beautiful, you can see how they would turn off some boy readers. The series, a thrilling futuristic science fiction story taking place on a spaceship among the stars, has two strong protagonists at it's heart--a boy and a girl--and is a great read for everyone.
The third book in the series was published with the redesigned cover, and the first two were given new covers to complete the set. These new covers definitely make a move to appeal to either gender and, thankfully, don't immediately classify the story as a "girls book" from the first look. I admire this move to make the series appeal to everyone, because I know a lot of readers who would love the series. In this day and age of beautiful and artistic book cover design, "judging a book by its cover" is a worn-out phrase. Because it happens. How much better would it be for reluctant readers to not be turned off a story that would appeal to them because of a cover or label? I can see this opening up a wider world for scores of readers.