Books and bookshelves

I am a book fanatic.  In my basement where we have our classroom I have the room lined with bookshelves.  The question is how do you organize it so you can find a book when you want one.  At one time I thought about card cataloging them like the library does but I don't have that kind of time on my hands.  What to do then?  I separated them by category.  I have a shelve of all history books and they are on the shelf in chronological order.  I also labeled the inside of each book with a time period or date to help keep them organized.  The shelve of the classics I have alphabetized by author.  Our science books are organized topically and my religious books are separated by reference, biography/autobiography and then misc. My last shelf is fiction, just for fun and that is arranged by reading level and those books are labeled in the cover also, well for the most part. It isn't perfect but it works.