We have several thousand--I have no idea. Hubby thinks it's 10K, but I don't think it's that many, but he does have many small military books that are like 60 pages each devoted to uniforms, or planes, or other military subjects--there could be 10K. He mostly has SF and nonfic military. I think I have mostly mystery and US/European history. We also have space books, animal books, nearly one Ikea "Billy" filled with biographies (two shelves of travel at the bottom), linguistic books, two bookcases just full of children's books, a bookcase and a half of just Christmas books, a bookcase full of bound issues of "St. Nicholas" magazines, etc.