We have several shelves. My husband's books take up a whole one, and then there are 3 smaller shelves (besides my oldest sons' shelf in his room for his own personal books). (By smaller, I mean 6 shelves high, but only about 2-3 feet wide... not like our huge floor to ceiling and 5 foot wide that my husband uses).
One is for curriculum and non-fiction books. It's in our "school room" (which is just a small area off of the kitchen). The non-fiction (and reference... Dictionary, Thesaurus, Atlas, Bible reference, etc) goes on the bottom 2 shelves where all the kids can reach them easily. My main curriculum that I use everyday (and lesson plans, etc) goes in the large middle shelf right at easy reaching level for me w/o reaching up or down too far, with workbooks & other frequently used things on the next shelf up. (These 2 shelves and the top shelf are usually "teacher only"). Then on the top are all the readers we will get to this year, but aren't ready for yet.
The 2nd extra shelf is in the hallway for the kids fiction books, comic books, and other chapter books. (My youngest has a row of picture books on my husband's large shelf 2nd from the bottom). The top shelves are for teen reads (Henty books, adult fiction and older teen fiction books), then as the books get for younger readers, they move to the next shelf down. (But this shelf is all for kids who are reading chapter books). There is one shelf in the middle dedicated to biographies & non-fiction for the older kids. The bottom shelf has our very large picture (like coffee-table) books that sometimes we use, but not often.
Our last extra shelf is in my room and is for my personal books- homeschool reference, family & parenting, my fiction (which I only have 1/2 a shelf for now since mostly I use the library and only read a book once anyway), devotionals, etc.
I guess we do have one more by the computer for my husband's "computer" reference books. (another 5 shelf, 2 1/2 feet wide shelf). The main one with my husband's books has books from college, linguistics books (his major), Bible reference, etc. that he refuses to get rid of. But it's rare someone will pull a book off that huge shelf.
And if you really want more details, our kid picture books (the ones on the shelf shared with my husband) are organized by hard-back/paper-back/board books & then by size, so that same authors end up being together (like all the Clifford books). Our non-fiction books on our homeschool shelf is organized by topic... like science: weather, animals, human body..... , History, Geography, etc. So if they want to find a book about bees, they know about the area to look. (or at least I do).
And if no-one touches it for a while, we get rid of it. We have so many books the kids haven't read, but they still prefer the library.
Hope that was helpful. But ultimately, you'll have to figure out what works for your family.
