It's so simple: Rethink your "library" and mix books and toys.
Typically, when children are young, it's easy to tuck baskets of books in corners, on coffee tables, and on the toy shelves. I find that when books are stored in many places--and not just on one bookshelf-- they are used more frequently.
In my classroom, our classroom library had two sections: one L-shaped section that housed fiction and leveled books around our meeting area (I like to think that the books anchored us) and a nonfiction library in an opposite corner. Personal book bags were also in table bins. No matter where you were, books were visible and accessible.
At home, I make sure that reading materials for all interests are on the coffee table, on bookshelves, tucked along with toys, in the car, and on the sun porch. Fran just got a new shelving unit from IKEA and it holds books and legos and toys and awards and special photos and tchotchkes. And since he helped organize it and can find the books he needs (or have them find him), he is reading more.
If the books are accessible, the the kids will find the books. And I love to find them when they've lost themselves in a good book.