There are lists with YA bestsellers. What they don't tell me is which books are bought by girls, and which by boys.
Are there any resources showing (YA) bestsellers by reader's gender?
I found this interview with the president of the Young Adult Library Services (YALSA), a division of the American Library Association (ALA). She mentions that there are very few male readers of YA fiction, but that boys tend to read nonfiction on subjects that interest them.
I've attended YA writing panels at SF conventions, and almost all of the published YA authors attending are female. Their work tends to have strong romance elements, which I'd guess would appeal more to a female audience. A couple of them also mentioned that their sons don't want to be seen reading books with 'girly' covers. These authors would be considered more 'midlist' than bestsellers.