A few days ago, the New York Times posted its list of top picture books for the year: http://www.nytimes.com/interactive/2015/10/28/books/review/28-new-york-times-best-illustrated-childrens-books-of-2015.html?_r=0.
And now Publisher's Weekly (PW) has weighed in. Here are links to their top picks:
YA: http://best-books.publishersweekly.com/pw/best-books/2015/young-adult n
Note that Nimona, Challenger Deep, and Bone Gap are also finalists for the NBA.
MIDDLE GRADE: http://best-books.publishersweekly.com/pw/best-books/2015/middle-grade
Note: The Thing about Jellyfish and Most Dangerous are also finalists for the National Book Award.
PICTURE BOOKS: http://best-books.publishersweekly.com/pw/best-books/2015/picture-books
One final link for now. Kate Messner posts this blog each year as the lists begin to emerge. It is must reading as well: kate messner what happened to your book today?