Its many quirks, and the author's style make this a worthwhile read.
Plot
The Princess Pea (human) has been taken to the castle's dungeon by a devious rat named Chiaroscuro and the confused Miggery Sow (also a human). It's up to Despereaux, an outcast among mice, to save her.
Morality
Despereaux is the only truly "good" character. Chiaroscuro is the "bad" character, but his situation is addressed. The other characters are either somewhere in the middle, both helping and hindering the hero on his way, or they are not in the story long enough to be good or bad. The story deals with light and darkness, and how stories are comparable to light, because they bring light to our darkness.
Spiritual Content
Despereaux has a dream about a knight fighting darkness. He later realizes that he's the knight in shining armor.
Violence
Both Despereaux's and Chiaroscuro's tails are cut off. Two people are threatened with sharp objects, but neither are hurt. Miggery Sow's so-called "Uncle" beats her.
Drug and Alcohol Content
None, none at all.
Sexual Content
There is romance, but it never goes that far.
Crude or Profane Language or Content
The only things that get close are a few exclamations of "Gor!" and "Cripes!". But that's about it.
Conclusion
This isn't your typical "Save the princess" story. The plot is like a web of all the character's lives woven together, complicated, yet easy to read. The author will follow character #1 until she has to mention character #2. So she backtracks to where she left off with charrie #2 and goes from there. An interesting style which keeps the pages turning. This is an overall bittersweet book with a superb ending (as well as a good beginning and middle).