To my knowledge, there are no images of the book covers yet, but I have just found out about some movie tie-in books for Barbie: Star Light Adventure and Barbie & Her Sisters in a Puppy Chase. Look out for them later in the year, when there will be book covers, and perhaps some content previews and plot information!
Star Light Adventure
Barbie Summer 2016 Movie Pictureback - Jul 26, 2016 | 16 Pages
"Children ages 3 to 7 will love this full-color storybook based on the latest Barbie™ movie, releasing in fall 2016. Press-out paper dolls and over 50 stickers are included to add to the fun!"
(Available Formats: Paperback and Ebook)
Barbie Summer 2016 Chapter Book - Jul 26, 2016 | 64 Pages
"Children ages 6 to 9 will love reading the whole story of Barbie’s latest movie, releasing in fall 2016. This easy-to-read chapter book features full-color illustrations, a sparkling glitter cover, and a collectible bookmark!"