You can use Freepik images as main element for the cover of a book as we understand this as a secondary element of your product, since the content of the book would be the main element.
If you want to use our images inside of the book, you need to make sure to use only a few of our images and not as main element, that is not on the full page but rather as small additions to the text in the book. The resources used inside a book need to act as a supporting element of the book content. For example, in a book about traveling, you can use the picture of a beach or a landscape to illustrate the text.
Some usages not authorized would be coloring books, children books, or any other similar publication where all the illustrations/images are from Freepik, since these would be the element that would catch the attention of the clients to buy that specific book and therefore it would be considered main element.
If you are a Free user, the attribution needs to be added to the book. This can be added to the credits section. As a premium member, you don’t need to credit the author when using the resources, but please remember to download the licenses.