Shelf: "A flat tablet or ledge of any material set horizontally at a distance from the floor, to hold objects of use or ornament"
No, this is not really a "trend", but these ARE trendy shelves, or "book holders" or "wall organizers", or whatever you want to call them. Gone are the days of a simple shelf on the wall: you know, the kind with brackets that never seemed too steady and sort of moved from side to side if you put anything too heavy on the shelf. And, of course, there was often just the shelf: no ends of any kind so no, you couldn't really put books on them anyway! These new shelves are just plain cool... and fun, and colorful, and they work!
Then there are what I call "floor shelves". These are trendy, hip, fun, made of all sorts of new materials and hold so much more than books.
And, of course, with your shelves it helps to have some Book Ends:
Here's a contemporary look:
You might also want to take a look at RoomRemix-The Blog for PK's post on "Accessorizing Shelves/Bookcases": you will find some great ideas and photos of bookcases and storage!