$20 to spend on overstock.com for only $10

Does not look like it is stackable. Way back when it used to be able to be used on books but not any more. Click on the fine print tab to see all the exclusions:

Limit 1 per customer • Voucher may only be used to purchase goods or services under the shopping tab • Voucher may not be used to purchase gift cards or cellular telephone plans • Excludes orders comprised of products from Books, Magazines, Music, Movies, Games, Electronics categories as well as items within the cars, travel, insurance and gold redemption categories • Offer value cannot be applied to shipping • Except as required by law the voucher is non transferrable, not redeemable for cash, and will not be replaced if lost or stolen • The voucher cannot be combined with other discounts, coupons, vouchers, promotions and promotional codes • Merchandise purchased with this voucher is subject to Overstock.com's return policy. see Overstock.com for details • If you return your order you will only receive the paid value of the voucher and not the promotional value • Voucher may only be used in conjunction with US orders not valid on international orders • Entire value must be used in a single visit • Other conditions apply

PAID VALUE EXPIRES ON NOVEMBER 20, 2017
PROMOTIONAL VALUE EXPIRES ON FEBRUARY 11, 2013