Half.com's return policy can be dangerous. You may not be refunded for a purchase even if there is a legitimate reason for a return (wrong item, item not as described, etc.). The way it works is the buyer contacts the seller through Half.com for a legitimate reason for return. If the seller agrees, Half.com gives the seller only 10 days to issue a refund. After which it is not clear from their policy how refunds are handled. In any case it is still entirely up to the seller to refund the money.
In my experience the book I received was diffrent than what was listed (another tip: be careful with books that have different editions). I reported the problem and got a response from the seller through Half.com initiating the "10 day window" for the seller to refund me the money. The seller decided he would not refund the money until the book was returned to him. So I returned it with USPS Delivery Confirmation in that short 10 day window. After 8 months I still have not received a refund or an explanation from the seller.
In summary, the transparency of the Half.com return policy is not clear, so buyer beware.