Build bookcases that are 27 or 36 inches high. Larger units are also used. Some of them have five, six or seven shelves and are between 60 and 84 inches high. The average depth on these bookshelves is usually 12 inches, but in places where space is tight, 9 inches may suffice.
Construct bookcases with adjustable shelf heights. You may have an array of books and magazines with different heights. In addition to the 9- and 12-inch shelves for books, you may want 11-inch shelves for magazines.
Arrange your bookshelves with proper spacing. According to Shelving For Libraries, fiction books need 10 inches of depth and you should not place more than eight volumes per linear foot. Encyclopedias need 12 inches of depth and you should have no more than six volumes per linear foot.
Make sure your books are not stacked higher than 54 inches above the floor. You want your family members and guests to be able to reach all reading material. If you are using taller bookshelves, it is usually best to put decorative items and things that won't be pulled off the shelves frequently on the higher levels.