Description Pop It in the Sack . Den the dog has a sack. Follow Den as he pops the things he finds into his sack. Go, Ken, Go! . Go, Ken, go! Ken is running late to a party. Can he make it on time without getting into a mess? The phonemes /ck/e/ are featured in this title. Level 2 - Red books introduce simple letter-sound combinations. As each set of letters is introduced, children are encouraged to use their new knowledge to sound out and blend words. For example, they will learn to blend the sounds s-a-t to make the word sat.