I arrange my books by genre. :3 Fantasy, horror, non-fiction, westerns, etc. Each genre has its own shelf.
I don't arrange them by author, although, I want to. I've been meaning to purge and do this. I know this will take me hours to do.

I have my 'queue' books pulled out just a hair, so I remember to pick it up next when I put a book away. :d I have a lot of read and unread books. Too many, maybe. -shrugs-

How's your shelf arranged? C:

that makes sense. I think that's how I started. :3
My shelf space grew with my book collections. lol. cx

That's my current problem. I have a lot of random stand-alone books. Which is fine and all, but a lot of them I haven't read. I want to get a box and donate books I won't be reading to our local public-library boxes. 'Free Library'. Some parks around here have little boxes to stick books in and you can donate or trade or take from.

When I had books, they were organized in a general by-genre section. Most of the books I have now are textbooks, and the books for pleasure are on a kindle which makes things so much more manageable for me.

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Not gonna lie, there for a while it was by the Dewey Decimal System. Now, it is more by genre. I try to keep like items together. I also watch out for the weight of the books and so larger or heavier books or book series go near the bottom of the shelves and lighters up top. Most of the books I own are read 100%. I would say 75% of my books have been mostly read. The remaining 25% have been opened, sniffed, and most likely are used for reference or for specific information.

@Totalanimefan: lol - I noticed! You keep making new topics. That's usually a good thing :3

I forgot to mention that my unread books are usually stacked horizontally in front of the other books that line the shelves. And that most of my reading is on the kindle these days. Those books are not so organized XD

@Totalanimefan: Yes, it's quite simple and very practical. It keeps my unread and "want to read" books immediately in view - if I put them in with the other books, I'd probably lose them XD Some of my reference books get stacked sideways on the shelves too - especially if I am using them a lot at a given time. I love the kindle for the immediate ability to get and read a book, and for not having to deal with a book light or background light (important since most of my reading is at night).