You'll make very little at a car boot sale. People want an armful of books for a few pennies. ebay is the same, by the time you've paid postage .. and I believe there's a maximum postage charge on ebay that's not very high.. and paid fees, you'll net very little. We're in the same position as you, not only do we have hundreds of books but my husband has a lifetime's collection of American comics dating back decades. Nobody wants them these days. We were thinking of Freecycling our books with provision that they go to a worthy cause or to a school or OAP home or something similar. The problem with Freecycle is that people sometimes spin you a yarn about wanting something for charity when they simply intend selling your wordly goods on. I agree that a garage sale might be worth trying, but it may not be worth the effort. Sadly nobody seems to want books these days.