It has a very children's-book charm in its innocent protagonists and watercolor style. The dominant color of this piece is a bright sky blue emitted by the spider's eyes, making a scene that could have been terrifying into something much more heartfelt. This mood is what makes this piece so amazing.
Bold and unusual choices have been made for the spider's design. His forelegs appear to be denser and more durable then the rest of him, presumably so he can smash his legs through the cave walls. His mouth and head shapes are cool and unique, as well as the previously mentioned eyes.
The trio facing the spider are distinguished by their body language. They all appear to be small children; a small girl, a slightly older boy, and a baby.
The boy is clearly the boldest of the three, being the closest to the spider and staring into its face. The baby views the boy as a protective figure and holds on to his leg. The boy holds a lantern in one hand and the girl's hand with the other, suggesting he is a heroic, guiding character. He holds the lantern high in spite of the fact that its light is negligible compared to the light of the spider's eyes.
The girl is the most timid of the three. She dares not look at the spider, and instead fixes her gaze straight ahead. Her knees are slightly bent, suggesting that she is either weak with fear or eager to run away.
The baby, in my opinion, is the most sensible of the three. The baby looks up at the spider with the same curiosity as the boy, but the baby is also afraid, like the girl.
I could, of course, be misinterpreting everything, but this is just what I see when I look at it. The lines do not restrict the colors, and coloring outside the lines has been encouraged. The art style is fantastic, the story is mysterious, the characters are told with distinction and subtlety, and the atmosphere is an innocent, heartfelt, enigmatic, ominous and awesome experience.
I know I ramble too much, but when I review things I like to address everything I see and thoroughly interpret it for myself.
TLDR: This is a beautiful piece. I really love everything about it.