They are everywhere now and for no good reason; thrillers, mysteries, adventures, fiction, non-fiction, you name it. A writer is stuck and has run out of ideas on how to move his story forward and boom! A love triangle surfaces which ends up being half the book. Love triangles are a powerful plot mechanism when the plot is in fact the love life of the main characters. Anna Karenina is a good example here. Pride and Prejudice is also a good example of when a love triangle works. But in The Hunger Games series for example, the story began as a very sophisticated and thought-provoking examination of our society and especially the corruption in the media and our obsession with entertainment. All this through the eyes of a very smart, strong-willed, and extremely likable female lead. How did this very interesting plot end up being a "who will she end up with?" story and who do I have to kill to make this shit go away?! (I don't like criticizing other authors and I usually avoid it. I have made an exception this time because I believe an example was needed to make my point clear.)
b) Front covers in which the author's name is ten times larger than the title.
This is basically the publisher telling you that the author of the book is more important than the book. This only makes sense if you're reading a biography or general non-fiction. Otherwise, it's just another marketing scheme, a way to make the author's name stick in your subconscious. Personally, the cover of a book is very important to me. I am in love with the visual arts and I do judge a book by its cover. When a cover is overwhelmed by the presence of the author's name written in giant, bold letters that take over half the surface of the cover, I feel a giant "ego" floating around in the room... and it's not mine.
c) Stuff and people coming out of nowhere to solve everything.
"Deus ex machina" in Latin, or "ἀπὸ μηχανῆς θεός" in Greek (they invented this plot technique) or "who the fuck is this person and what is he doing here" in English. You know what I'm talking about... "experts" and "specialists" who appear mid-way through the story in order to give you all the information you need and then exit the story as suddenly as they appeared, never to be seen again, or simply die in the following chapter because there is no more use for them in the story. Or the dead victim who miraculously isn't dead after all and crawls towards the killer and stabs him in the foot so your character can escape, and then the killer kills this victim again... for good this time. This technique was cute for about an hour, two and a half thousand years ago. Now it's just exhausting to read.