To see the books cover that you exported, first you must have bought the PREMIUM plan.
After that, you can just create a new Visualization of your database of type galery and in the layout settings put the Card Preview as Page Cover and the Fit image enable.

Change the Book Title
If you change the book title, kindle2notion won't be able to identify new bookmarks associated with a already exported book. So If you pretend to add more bookmarks for a specif book, don't change the book title.
Change the Bookmark quantity
We need this field correctly to identify if a book has new bookmarks or not
Disconnect KindleTwoNotion of your page
Remove the database
If you delete your database you will have to connect your Notion workspace again in the KindleTwoNotion platform
To get the book cover, we use the Google Books API. If your book doesn’t have a cover, it means that Google Books didn’t return a result for the title 😟.
But don’t worry, these cases are rare!
Anyway, you can upload the book cover directly on Notion without any problem as well.