Another great entry in this wonderful series for young chapterbook readers. I'm really enjoying these books and look forward to each new volume. This one is not my favourite compared to the previous three but it holds it own and progresses the story well. As we can tell by the title of this one, the villain takes more of a major role this time around as the heroes search out their quest for another magical item and the last of their missing Olympians. A fun story with lots, and I do mean a lot, of action. Introduction to more Greek mythology and one I particularly like about this series is the emphasis on the Titans, which are often harder to understand. Many children's books start with the Olympians, glossing over the earlier Greek mythology of their origins. This book has a definite feel of being the end of the first story arc. By book's end we have accomplished one of the missions set out in the first book, gather together the six Olympians (3 boys, 3 girls). New information is imparted to the group and while some open threads continue, new goals are also added. This leads me to believe we are in for a long running series, like Holub's other series for girls "Goddess Girls", but one which will group books together in story arcs similar to the Magic Tree House series. If so, I'm game and in for the long run. Highly recommend this series for libraries!