Book Sale

So I've got a confession to make, DIY and thrifted clothes aren't the only thing I collect. I'm also pretty addicted to books. In the 3 years I've lived in London, I've managed to absolutely fill the house. Knowing I would never send them home, other than a few cute ones given to me by friends and family, due to how much they all weigh, its time to de-clutter. The wardrobe overhaul was just a start. I need to sell all these books (its a pretty well organised collection - no dan brown's I promise) but I don't know where to start... Does anyone have any tips on how to do it. Was contemplating markets or car boot sale. Any ideas?