Don't go overboard decorating your bookshelf. Pick your inspiration piece and use the colors from it to build on your collection. Accessorizing your space is just as important as the functional pieces appointed for the room. You can easily add contrast by using artwork, a series of books, floral arrangements, sculptural objects, and gifts you've received that are worth displaying to add a degree of sentiment on to your shelves.
As a Designer, I live by three design principles and use them in all my design efforts to achieve a well appointed space; one part old, one part new, and one part nature which can be natural light, plant life or natural textures. Take the same principles and apply them to decorating your tabletops, bookcases or fireplace. But most importantly have fun with it and most importantly let it reflect your own style!