We’ll start with Romance, because it is the best paying genre, period.

This seems to be a supernatural romance.

Note that this book is a “picture cover” with the hot male chest (the face is cut off.  This is common in romance) and the wolf, which indicates to me “paranormal romance.”  There’s usually an animal and a half naked man.

I’m not a font maven, so I can’t tell you what the font is, but it is a fancy font for the name, and the name is featured and about three times as large as the title.  You can see that name even in thumbnail.

Yes, the author is a bestseller, but frankly, just seeing a name that size, without thinking, the reader will think “bestseller” so there’s no reason for you not to do it.  It’s not a conscious thing, it’s beneath the thought process, so you’re not really lying.  You’re just conveying the impression that you’re big heap writer and increasing the chances they’ll buy.

Note the “old time” hairstyle, (face again missing) and the font, as well as the author’s name in a golden shape.  This is likely a regency (I don’t read much romance, but if the cover isn’t on a regency, they’re signaling wrong.)

This is a contemporary romance/thriller.  Note that it’s still a photo cover.  The rose, and the shattering vase indicate romance and danger.  Also, the romances with elements of thriller often have these spare minimalist covers.  Again, note the author name on top.

Something I’m noticing looking through these, that even I never saw before, is that everyone says “a novel.”  I don’t know if this is now in all fiction — an artifact of the digital age, where “a book” can be a novella or a short story — I shall keep an eye out as we move on.