One of the things that I really like about bookstores is that they do faceouts. This means that they turn the books so you can see the cover art, rather than the spine labels. While this isn't totally practical for a library setting, why can't you take the 10 copies of each Rick Riordan title and flip them to show the covers. In addition to giving the section some interest, you will actually save shelf space.
If you are at your local Barnes and Noble, definitely take a walk through their teen section. They have taken faceouts to a new level.
Almost the teen entire section is faceouts. As we all know, cover art makes or breaks a book sale and the same is true in libraries. This is great for a browser, but difficult for a person looking for a specific book. It took me 10 minutes to find a copy of Divergent by Veronica Roth and I know what the cover looks like!
Where we can put this into practice is to make each shelf on an empty range a different display. In the picture above, each shelf sign gives a different category of popular titles. The top shelf includes the bestsellers. Another shelf includes great books for girls. If you want to see what this looks like in a library setting, check out Storytime Katie's Tumblr post from May where she created a bunch of "If you liked, then try" shelves.