It’s not too late to give an ebook gift for Christmas to the readers on your list. Amazon makes it very easy to send a book and even let you set the date for it to be announced via e-mail. This post gives step by step instructions on how to do that.
But, the question remains, what book? So here are some suggestions from books I have read and loved over the years in multiple genres (many are not reviewed on this site because of how long ago I read them). Each book listed is both clean and one I have rated with 4 or 5 stars. I am still building these lists in Amazon, but this should give you a great start.
For more ideas, you can filter above by rating or by genre for books I have specifically reviewed on this site.