I have a book shelf about their height (age 2 and 4 if that's any indication) the shelves aren't too deep. So they can see exactly what they want to get. The lower shelf hold their books.
I also have a toybin (yes, bought a target.) It has bins sorta slanted so you can see what's inside. I have this in their closet, so I can close the door if it looks too messy. But, it really does stay neat in their room if you can believe it! EAch bin has it's own kinda of toy. So, I can say put this in the dinosaur bin. I really like basic toys so their bins include; ball bin, airplane bin, tool bin, dinosaur bin, animal bin, sea animal bin, car bin.
I am thinking of getting a book shelf that will hold their books out, so they can see the title and front of the book.