…will use a random set of book covers downloaded from Amazon Japan’s “dirty stories for men” collection. Not the trendy manga/anime-style covers, but the more realistic airbrushed cheesecake style many of them use.
The title of this little gem, もっちり熟尻, breaks down into a current slang term for “firm texture”, followed by a kanji meaning ripen or mature, followed by the kanji for buttocks, translatable quite effectively as Firm Ripe Ass. This is not the least subtle title I’ve seen; that award would probably go to ごっくんOL (mouseover for NSFW translation).
[side note: I’ve noticed a lot of invented-word kanji combos in genre titles, and I suspect many of them are wordplay. In this case, 熟尻 might be read as jukkou, which when written 熟考 means “deliberation”]
Other covers I’ve liked in this genre include Wife-play, Temptation Paradise, My Aunt and Me, and Welcome to Honeyfun Island. I’m not terribly interested in the books, mind you, but I do like the cover art. [Update: and another, Saucy Sister-in-law (literally “with extra sauce”, usually used when ordering beef bowls).]
Not all of the artists working on these books are equal, of course. Welcome to the Honey Garden is a poor sister to Honeyfun Island’s main attraction, and Beloved Kindergarten Teacher isn’t as well-drawn as The Naughty Kindergarten Teacher, but there are a lot of these books available (as I first discovered here and later here), many with quite pleasant covers that are considerably classier than this vintage American example: