Meyer skillfully entwines her original ideas with Carroll's established ideas to create a fully living world. The sprinkling of Carroll quotes, and the visits from Wonderland friends, are a true joy. The characters were fleshed out, with believable actions and reactions. The prose was well-written, and drew the reader into the plot quickly.
The reader knows, before starting the book, that Catherine will become the Queen of Hearts, a passionately miserable individual. The strain of melancholy that is woven through out the book purposefully keeps the reader anxious--it's always in the back of the mind that happiness is not the ending for Catherine. I must say that Meyer did not disappoint, and delivered a heartbreaking ending that left me in tears.
Overall, I can find no fault with Meyer's beautiful, tragic novel, and recommend it wholeheartedly.
Note: I do think, though, that readers will enjoy Heartless most if familiar with Carroll's original tales. I paused a few chapters into the book to reread both Alice's Adventures in Wonderland and Through the Looking Glass, and was extremely glad I did.