I've spent all weekend, literally six hours each on Saturday and Sunday, organizing the books in my bookcases around the house. Taking in to consideration the amount of time I put in to just getting things loosely sorted so I can see things better, I thought I would put a few minutes in to a post about keeping your library organized.
I have too many books. Once you have three layers of books on the same shelf, you will never know what is in the back two layers, or the few books perched on top. My way of combating this is simple, I put all the one off, lesser known authors in the back. With those books, any new or non series paperbacks get tossed in there with them. If I'm pretty sure that I will not be completing a series, or it is not a desirable author, then you get to the back of the bus. My advice is to buy more bookcases until your significant other gets pissed, then get one more for good measure.
If you have under 500 books in your collection, alphabetizing may be an option for you. The question remains, do you split up the series if they have different authors? Do you keep all your Del Ray books on it's own shelf? What about the yellow cover DAW originals? I kind of do both, depending on what I'm looking for at the moment. Moorcock, you get your own shelf, but if it has a yellow cover, you go with the DAW's, because I'm after those right now. Asimov, your all alone in your triple stacked glory. No real answer here.
I'm a complete nut for Forgotten Realms. Each of these series of books has series within them, and sometimes another one to spin off of that. Example: The Harpers, and the Finder's Stone Trilogy, which both have books that cross over in to the other series, and back again, and have several spin off series, one off books, etc. It's a mess, but one I was more than excited to tackle in 11th grade, 20 years ago. I read every single one. In these cases I just put the series together, and try to keep them on the same shelf, or layer, in the same book case. It's very satisfying to see everything lined up by number.
Stickers, gunk, pencil marks, even pen needs to be taken care of when you are organizing your books. Get a rag and eraser, some alcohol and set up a little prep station. Some may only need a light dusting, and once the shelf is empty, dust that too. The frequency you do this is up to you, I bet I clean off the shelves and look at my books every three months or so with my son. He likes to look at them and help me while I organize, which is great.
They are all different sizes, height and width, what gives? They take up a ton of room on your shelves, but man, do they look great. I have a great answer for hard covers; just toss them on the shelf in size order, and don't double stack anything that is above the bottom shelf, the shelf will bend over the years. If you can marry up a series or author and the size is similar, go for it. I typically do not buy hardcover books unless they are something special, vintage or first printing.
I make a few notes of books that I thought I had, but are mysteriously missing from library. This happens constantly. I was wondering if people were just borrowing my books when I was not home, but ruled that out. Dust jackets go missing, covers get ripped, I just write it all down as I see it, then when I'm in the wild I try and get those books to replace the abused ones I noticed. All of the above is especially true with my Piers Anthony collection; he frequently writes more Xanth books, books are re-released very often with new covers, some of his books are so old they are literally deteriorating as I dust them. I pride myself on having a complete Anthony catalog, but I'm no longer up to date, and I'm always on the lookout for better versions of the rarer, older books.
All pictures taken by me with a broken iPhone.