There are many different ways that you can organize and decorate your bookshelves. Personally, I organize by author currently but I am looking for different ways to organize. I have found many different ways to organize bookshelves and I will include what I can. I have also found a few different ways that you can decorate your bookshelves without them becoming overcrowded or cluttered.
Add storage bins to the bottom shelves of your bookcases. Or having your large coffee table books on the bottom shelves. The storage bins can be used to hold decorations you're not using, or even just using the baskets as decorations themselves. Keeping these heavy items on the bottom shelf is always a good idea, you want your lighter items to be higher up.
One way to organize your books is either alphabetically or by genre. Personally, I like keeping all the books by the same author together and then organizing them from there. When organizing this way make sure that you are keeping the series together as well. So if the author has two different series and then a bunch of single books I would suggest keeping the single books between the two series and keep the series together.
Utilize stacking. Your books all don't have to be placed vertically, stacking your books horizontally creates a different look for your bookshelf while also using less space horizontally while utilizing the horizontal height. Many of the pages that I have seen say that 70% of your books should be vertical while the other 30% should be kept horizontal.
If you are someone who really likes color another way that you can store your books is by using the rainbow effect. Organize your books by color, regardless of genre, author, etc. The pages that I have seen say that you should keep the darker colors at the top and then get lighter as you go down.
Your favorite books deserve the prime spot. Many pages suggest that your favorite books should be front and center on your bookshelf. These books would include any that you always reach for, your favorite rereads, or just your favorite overall. This works the same as keeping a space for your unread books, keeping them in a certain spot before adding them to the shelf where they belong. Books that aren't used very often or are never read keep them on the top shelf.
Try organizing by height. Maybe keep tall books on the edges and go shorter in the middle, or alternate shelves starting with the tallest book, then the shortest, and so on.
One fun way to decorate your bookshelves is by adding wallpaper to the back of your bookshelf. This adds a pop of color (if you so choose color) and it can create depth to the shelf as well.
Add your family heirlooms, pictures, vases with flowers, travel trinkets, etc. Over-styled bookcases can look a little cold, while meaningful items will automatically inject warmth and personality into the room.
Utilize decorative bookends. Your books don't need to span the length of each shelf. Use bookends to keep space for adding other trinkets.
Layer your bookshelves. (above picture) This means starting each shelf (working your way down) on opposite sides. This helps create a different visual, while still adding something different to your decorating.
These are by no means the only tips and tricks out there. There is tons of information available on the internet if you really want to organize your bookshelves. I'm getting a new bookshelf for my birthday (haven't gotten it yet) and I want to be able to use these tips when I get it so that I can really make my bookshelf a focal point.
You don't have to have all your books on your bookshelf at once. If you plan on storing some of your books, make sure that you look up the proper way to store books without damaging them.