Where shall we start? Let's start with trees, a common enough image on covers, with their useful symbolism of roots, shelter, family, complexity. Then add a beguiling figure, in silhouette, so as to leave the reader's imagination a bit of space.
Now let's use the silhouettes on the cover of this Lionel Shriver novel as a bridge to our next theme:
But I like this version, which I think is very stylish:
A further variation is the torso shot:
As the theme gets more and more common, designers get bolder, cropping off more and more of their models' bodies...
There are refinements of the basic themes to look out for too: wooden boards are very popular (very Instagram) -- see the Steinbeck cover above and these variations below:
And what's that? A teddy? Ah, the universal symbol of the vulnerable child, used far too often for a treacly sentimental effect:
Some authors' books have appeared more than once in this very unscientific survey: Heather Gudenkauf (who I hadn't heard of previously), and, in particular, Diane Chamberlain. Her publishers win the prize for including every current cliche of book cover design on her series of novels. Yes, she definitely wins the prize -- she even has the cliche of cliches, the butterfly trapped in a jar:
Notice that several of these tick other boxes as well: headless child, wooden boards. I guess publishers want to achieve a current, Instagrammy feel on their covers and perhaps also want to signal that a new book can be bought on trust because it's 'just like' that Jodi Picoult novel you enjoyed so much last summer. Hmmm.
Finally, just to reassure us that not all book covers are following the same rule book, two covers that I've been strongly drawn to every time I've been in a bookshop recently: different, more original (though pastiches, I guess):
Next time you're browsing in a bookshop, see if you can spot more headless bodies and severed limbs...