First: Stock assets are meant to be used, so sure, you can use it, with one exception: if the asset is marked editorial use only. So, it depends on the asset.
Second: an extended license is only needed when the primary value of your book lies in the cover image. If not, a standard license may be enough. Check all the conditions.
Third: Editorial use only assets may probably not be used for your book cover, except if the book is non-fiction and treats the exact subject of the picture (like a book about Apple, and an Apple device in the picture).
Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).
AdChoices