After doing some reading this weekend I came up with two.
1) Fiction. Really interesting story that was told from a child's point of view, but with serious things going on around her. At many points it was cute and clever. However, there were some important things that I felt like I was supposed to understand--like who the kid's biological parents were, what happened to the villain at the end, etc.--but didn't, because the kid could only convey what she heard and saw, and the adults tended to ping looks at each other in an attempt to be discreet. Great for the kid, not so much the reader. I'm not very good at reading between the lines.
2) Non-fiction. I was reading a book that relied heavily on illustrations. And the illustrations were not located next to the text that discussed them. This bothers me in a lot of books. These were black-and-white drawings that were embedded in the text, and they all seemed to be at least two pages away from the text describing them--like I'm reading the text and have to constantly turn a page, or two, forward to the figure, then back to the text. They always seem to be after the text describing them. I'd much rather have them before. Like, "Here's the figure. Now let me describe what you should notice in it." But most non-fiction books I read seem to be more like, "Here's a text description of an abstract phenomenon. Got it? Okay, now here's a picture of what you should have been imagining from the text."