I did have similar situation several years ago and my textbooks/professional books donated were scientific at graduate level or above, meaning not depreciate that quickly. I used amazon.com and barnesandnoble.com websites for evaluation because ItsDeductible doesn't have value for professional books. Only textbooks for elementary school thru high school or lower level college would sell $1 each. Advanced textbooks typically not available at such a discount.
But IRS auditor took a significant deduction without any explanation on the source of evaluation, which certainly resulted in an appeal.
