I think Candy covered it all.

Some time back Kathy estimated I own (she refuses to take responsibility for
any of this) at home, 7000+ books, which is a bit more than 100' of shelf
space. My method of filing is to know almost where 80% of the books are in a
mental map -- which only works if you are the sole mental that cares to find a
book. Clumps of books are arranged by category as whimsey and Saturday morning
dawdling dictates. Business books on one shelf, UFO books in the bedroom,
fishing and camping in the front room, writing manuals in the livingroom,
gardening & computer books upstairs, Atlases and railroad books elsewhere.
I've recently started concentrating on clumping the Chinese, American Indian
and Civil War. Though I am familiar with the Dewey Decimal system, I find it
too structured. My original concept was to leave the books mixed, including
our son's books in with the other books. The strategy here was that, though it
would make it more difficult to find a particular book, whenever looking for a
book the chances of finding something else would be increased. I consider this
an educational environment of discovery. Kathy seems to consider it a menace.

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