My husband and I love books. We secretly hope to someday open our own library, LOL. But, even so, we still cull book clutter from our shelves a couple of times a year. In fact, I usually keep a box in our den year-round just for tossing books, movies and CDs that we don't want to use anymore. Then, when we go to visit my parents or some friends, we take them to the big used bookstore there and trade them in for credit. Then we get new books, movies and music that we will like. Invariably, we come home with less than we went with, so there is an actual net reduction in the amount of stuff we have, but trading something you don't like for something you do like is always a good thing.
To make your shelves look neater, try arranging your books from tallest to shortest, or by binding color. While this isn't library-approved organization, it does make your remanining books LOOK neater. If you'll notice, a lot of thrift stores work on this principal, grouping clothes--especially shirts--by color. While it does make things easier to find--because when most people shop for a shirt, they're shopping for a specific color--the reason why they do it is to make the store look neater. People are more likely to shop at a neat store, and you also have less theft and people make fewer messes/cause less damage when a store is neat. The messier anything is, the less likely people are going to treat that area with respect. You can also get better prices for things which are neatly organized in a store; if a store is messy, people expect prices to be lower and will not spend as much money.
Something I still want to do, because I'm not a person who is fond of pictures, is scan all of my pictures and organize them using some sort of photo album software, and then throw all the hard copies away. A CD takes up a lot less room, and you can store it in a fire-proof safe or safe deposit box, so you don't lose them if something happens to your house. You can also store vital information with them--names, dates, relationships, etc.--and pull them out quickly to make into slideshows or print them for montages for class reunions or funeral services.
Although my mother has a neat wall in her bedroom, where she has a framed copy of one picture of each of our ancestors--as far back as the pictures go. When we move to a different place, I would like to get a copy of all of those pictures, plus add pictures in from my dad's side of the family, and arrange an entire wall in a living room or hallway with family pictures, and have them arranged so that they form a family tree (have my great-great grandparents' picture at the top and work down the wall until a picture of myself and my husband is at the bottom).