Pinkney's 2010 Caldecott Medal winner, The Lion & the Mouse, is a retelling--or, rather a re-showing--of Aesop's traditional fable by the same name.
As the story is traditionally told, a mouse is caught by a lion and pleads for her life by arguing that one day the lion might need her help. Although the lion scoffs at the thought that a tiny mouse could ever help such a mighty beast as a lion, he releases the mouse. However, the lion subsequently gets caught in a hunter's net, and the mouse--hearing the lion's distressed roar--ends up freeing the lion by nibbling a hole in the net. The traditional moral: "Little friends may prove great friends." Traditionally, then, the story is meant to embolden the meek ("You may be a great friend one day!") and to encourage the proud to look out for the little guy.
However, in Pinkney's version, the moral is not so tightly constrained, largely because the only words Pinkney uses are onomatopoeias---i.e., words that express sounds made by the creatures in the story, such as the screech of an owl, the squeaking and scratching of mice, and the roar of the lion. This textually minimal approach lets the story breath in new ways, broadening the possibilities for the story's moral.
While the range of possibilities still includes the traditional moral, in my view the most obvious teaching of Pinkney's version seems to be that mercy is a virtue. In other words, the moral of Pinkney's version is that mercy is a good character trait that human beings ought to embody. I take the developmental value of the book for children to lie chiefly in this teaching.
Several aspects of Pinkney's version shift the book toward this interpretation. First, since there is no dialogue, we do not get the lion laughing derisively when the mouse suggests that the lion may need her help one day. Rather, all we see is the lion letting the mouse go free, which looks more like an act of mercy than an act inspired by the lion's arrogant amusement (as in the traditional telling). Moreover, as a result, the mouse's liberating action looks less like mere payback and more like mercy as well.
Second, Pinkney's illustration of the families of both the lion and the mouse at various points in the book adds a new dimension to the story: the merciful actions affect not only the individual to whom mercy is shown, but also the wider community. In other words, if the lion had not been merciful, there would have been a nest full of baby mice without a mother; if the mouse had not been merciful, the lion's mate would have been forced raise her pride alone. Much more is at stake than merely the lives of the individual lion and mouse. Here, then, are the deep familial and communal roots of virtue. Pinkney's story teaches us that the value of mercy lies not merely in benefits to its bearer, but also in benefits to the wider community. Surely this is a moral lesson worth teaching.
If the developmental value of the book lies chiefly in its moral teaching, its subjective appeal lies chiefly in Pinkney's stunningly beautiful illustrations. Pinkney uses a combination of pencil, colored pencil, and watercolor paint to produce illustrations that are loose and free, but that are also rich in detail.
Pinkney uses the background of the illustrated scenes to great effect in the story. For example, in the beginning of the story the mouse flees from a pursuing owl. Here the background of grassland, trees, dead logs, flowers, and night sky is rich and detailed. However, as the mouse stumbles upon the lion, the background setting becomes more minimal. When the mouse and lion stare each other in the eyes--at the lion's moment of decision--the background is blank, which focuses the reader's attention on the two characters and the gravity of the lion's choice. It is as if nothing matters at that moment except the lion and the mouse. As the mouse flees, the rich background scenes return to the illustrations, just as the mouse's life in the world returns to her. Pinkney uses the same brilliant effect when depicting the mouse freeing the lion.
In sum, I recommend Pinkney's The Lion & the Mouse without reservation; its 2010 Caldecott Medal is well deserved.