As with all of Lackey's work, this is a good read - I can't think of a novel of hers that I didn't like. However, this isn't one of her best. She seems to be going through the motions here - the villain is like many others, and there are more clever animals (although with more justification here, as this is a reworking of "Puss in Boots").
I am disappointed by the way the Elemental Masters series has developed. I liked the basic idea very much, but from novel to novel there seems to be little consistency. If they built up into a coherent whole that would be grand, but they haven't so far.