Letters to the Happy Camper: Write Now. Read Later. Treasure Forever. (Unique Letters to Send to Kids at Camp, A Book of Creative Keepsake Notes for Summer Camp)More than 2. 4 million copies sold in the series! Send them off to camp with love. Give your young camper this keepsake book of letters to keep them company and encourage reflection. You (or a group of loved ones) fill out the first part of each letter and seal with the enclosed stickers. Once at camp, your child will be able to open the letters and add to them, writing and drawing in their own thoughts, memories, and observations to create a souvenir