One of the super smart third grade teachers on our campus has a really great routine when she brings her class to our library: choose your chapter book first!
She herds the whole group over to the fiction section, has them choose a chapter book and bring it to her for approval.
She makes sure that the book is a good fit for their interests and reading ability. AFTER they've chosen a chapter book, they can spend the rest of their time choosing a non-fiction book, magazine, picture book, or more chapter books for their other two items.
Every day, her class has sustained silent reading time for at least 30 minutes. If a student doesn't have a chapter book that's a good fit, he or she does not get the best use out of SSR time.
In other classes, I see students spend their library time less purposefully, and then just grab the first chapter book they see. When SSR time rolls around, those students may be staring at pages they don't comprehend. They aren't moving forward in their reading skills.
I've really seen this little routine make a BIG difference with her students. Try it in your library, and tell me how it works for YOU!