Age and Topical. Contemporary Fiction, Non-Fiction, Classics, Juvenile Fiction, Middle-Reader, Chapter Books, Children's Books. Then break down based on quantity, Non-Fiction could be Political, Travel, Religious, Biographies, Sports, etc. depending upon someone's reading preferences. Keep them each in a differentiated area, either from floor to ceiling, right to left, area of room, etc. You can then refer to the general area and find a book within just a moment or two's glance, even with thousands in your collection.

A friend once rearranged using color. It was beautiful, but totally impractical for lending them out or finding them quickly.

I like to arrange my books by topic first, size second and color third.

Don't save every book you ever purchase.

I keep hard covers separate from paperbacks because of the difference in size they use different shelving, but otherwise both are organized by subject and genre. I recently started liquidating all my paperbacks, I do this periodically. If I find that I have re-read something often enough for the paperback to start falling apart, I'll replace it with hard cover. If I find that a hard cover hasn't been read in over a year, I'll re-read and decide if I want to keep it or trade it in on new books, unless it's a reference book like a dictionary in which case I keep it for a few years before updating it to a current edition. Language changes, so I update those types of reference books every so often.

Everything by one author together, paperbacks and hardcover. My husband's books are not mixed up with mine, though we overlap in taste somewhat. Kids books on a lower shelf. Dictionaries handy, reference books not used often can be on higher or more awkward shelves. Colour should have nothing to do with how you arrange books, unless it's all one topic and they naturally go together. You can break up the books with decorative items and make them all related in colour if that pleases you, but it makes no sense to organize by anything other than topic and author, and how often you use them.
I am incensed every time I see some idiot designer recommend covering books with pretty paper, basically hiding them. Do designers not read?

Nothing to add to Timeless Interior's comments. They are spot on and exactly what we do in our library. Put on the Music Man soundtrack, set it to replay Marion the Librarian until you are done! It is really fun to arrange books.
It is so refreshing to hear from someone in this digital age who still actually has books.
Remember, there is room for color, size, shape organization within the categories.
Regards,
Karen & Joseph
for Decorative Philosophy

Marry a librarian.

According to some sources they are quite passionate when they take off the glasses.....

Lots of great advice, but it sounds like it's coming from Mrs. Hughes or Mr. Carson on Downton Abbey. Those of us who live in moderate homes under 3,000 sq ft don't have walls of bookshelves reachng up to the 20 ft ceiling where we need a rolling ladder to access them.

You could do your "reference-type" books by topic (e.g. Travel, computer manuals). Keep Fiction together and then arrange those alphabetically. Then keep non-fiction together. Those could be further categorized by topic or alphabetically. Keep it simple or you won't be able to find anything.

Maryenidlareg I can think of one good reason to cover your books with paper and it is the same reason so many parents used to make their kids cover the school books with brown paper cut from grocery bags. It protects them from damage. Basically it can protect the binding which can fade or become brittle due to sun and exposure. Libraries with valuable collections often keep the most valuable books in complete dark humidity controlled storage to prevent the type of damage sunlight can do to bindings. However, if you do cover all your books in paper you need to label them so you can still find what you want! I used to work in a bindery and every time you have to replace the binding on an old book, they have to trim the pages. That means that things like library books that may be rebound multiple times eventually have no margins left!

In a strange kind of way, my books seem to be arranged by the time/circumstances in which I acquired them, which tends to bring like together with like. I have a couple of shelves of books I got to review at some stage of my life; mostly international hardback novels and the like I might otherwise never have read. I'm an editor, as some of my friends are, and some are authors -- all that tends to cluster together, too, together with some other South African works. I have a very shallow bookcase full of poetry paperbacks, play paperbacks, and odd little academic paperbacks. From student days of various kinds. Also from student days, a whole string of paperback lit crit novels along the top of one of my windows. Hardcovers mostly from graduate study days in another bookcase, with some books I inherited from my parents, and others I might classify as intellectual explorations of various sorts. Gardening, decor and cookbooks live together; they were largely acquired at a time when I could afford to indulge in such things. Ditto theatre and film books. Most of the coffee-table format books (largely art and arts) have a home of their own on glass-fronted shelves because they fit in there beautifully (flat, but they look good and happy together). Unfortunately a house mouse got in there once and chewed bits of the corners of some rather splendid books.

Heaven help anyone else trying to find a particular book, but it makes sense to me.

Haleydaniels those of us who read rarely have small collections. Last time I used a mover, I had over 9000 lbs. of books to be moved.

Oh, yes, and I have a collection of PG Wodehouse inherited from my brother which lives in a rather snazzy orange canvas shopping bag. And a few other odd bits here and there.

We have thousands. The non fiction are organised, the fiction are not.

Jessica, I'm never moving again for just that reason.

From a book seller : by subject, then fiction, poetry etc, by author. Within non-fiction categories I arrange by titlle.

I like these tea towels from the Library of Congress: http://www.loc.gov/shop/index.php?action=cCatalog.showItem&cid=3&scid=644&iid=5136&loclr=fbloc

Jessica, I've got hundreds of books myself, and give away more than I keep. I spend more on books than on clothes.

Me too! :) I'm having to drastically downsize my collection since moving into my new place. Hence the liquidation of the paperbacks and culling of the hardcovers.

I once did a major move to the other side of the country and gave books away like a madwoman. Now I think d..... d..... d.....!

Whatever classification arrangement you choose, allow for room to expand. Otherwise, there will be need for massive re-arrangement. We bit the bullet when we first finished our library/music room and gathered all the books that would go in that room. We underestimated our book mass. Added more shelves with some sections filling up within two years. That led to books getting filed in a more random than organized fashion. Cataloging with some of the online tools would be great, but beyond our time, energy and anal sphincter tone. If using high shelves, think about location- seldom used books in the nosebleed sections, more often used books in lower shelves.

Summilux, you just reminded me of something many people don't remember to do. Books are heavy and if you are installing shelving for them you need to take into account the load bearing capability below them just as you would for a large aquarium, a safe, or a waterbed.

chook, I did...50 years ago, and he is...but quietly so.

@Jessica- I hear ya. The bookshelves are supported by 1/4" thick by 1.5" wide steel squares lag-bolted to wall studs and screwed in to the boards. The boards are 1 5/8" thick which together with the interval supports makes sagging not a concern. While not an organization issue, some of the flimsier shelves I see limit the weight they can support.

First by subject, then by century, era, or nationality, then author's last name.

Edithsmom, quietly, he he!

Shhhhh.

OK, I know this sounds a bit odd..but I organize my books according to their predominant
"color" on the binding White- to creams, shades of blues from lights to dark, etc.
By color theme book bindings there is no rhyme or reason for what sits next to another. Hard or soft, fiction/non...it's a virtual pantone array at my disposal. It makes sense to me!

Honestly! I buy cofffeetable books (most collectibles) and I buy ebooks from Amazon for novels, etc. If I love it so much I buy a hardcover or paperback. Buy a Kindle or share the book once you're done. Otherwise arrange it by author as my suggestion

Having downsized from my "dream home" with bookshelves floor to ceiling in 2 separate rooms (my study & my living room) here is my book advice for book lovers --- I donated many boxes to our local library. Many, many boxes. I started writing down a dared list of everything I've read long ago in a journal - it makes it easier to share good books with friends or the library. I still have my absolute favorites and hope to add a floor to ceiling shelf soon but only one. Most of the books I kept are children's (I'm a teacher and now a Grandma.) low shelves for kids! Middle shelves for me & high for my tall husband.

The best part of donating to the library is I can "revisit" them! Obviously I did not move out of town. If the library did not have a copy, they kept it. Otherwise they sell extras to buy more books.

I love books - a lifetime of reading & trading & now sharing them.

I organize my books by topic. If I get more books and run out of storage, I make more storage. Books are important and nothing feels or reads like a real live book....just sayin' .....

We like to keep library books in a completely separate place in our hallway. Easy to find them when it's time to take them back to the library.

Us too.

yup i have a shelf by the back door for library books and letters to be taken to the post office.

If you have a library's worth of books try the good ole Dewey Decimal System and card drawers. Stock up on oil lamps and you'll be ready when the plug is pulled!