I have lot of personal course books and other books and some of them I sold on half.com. Is the income taxable and I need to pay taxes. Thanks for your help.

Selling personal property like this must be reported as a capital gain ONLY if the proceeds you received on the sale is greater than your original cost. If it is, then you have a gain equal to the difference between your selling price and your purchase basis. I would think that in the case of selling school books you probably received a lot less than you originally paid, so it's unlikely that you have a gain.