Author Suzanne Collins continues her excellent fantasy series, The Underland Chronicles, with a strong fourth book. When Gregor returns to the Underland he expects an uneventful visit with his friends and a chance to see his mother, still recovering from the plague she contracted during Gregor’s previous subterranean visit. Instead, he is plunged into a desperate quest to save the mice (or “nibblers” as they are known in the Underland) from annihilation. With an assortment of human friends, his little sister Boots, and the loyal giant bats and cockroaches, Gregor faces an avalanche, treacherous water, giant scorpions, and poisonous gas. As in the earlier books, his success depends in part on the solving of a cryptic riddle. Gregor continues to be disturbed by the rager aspects to his Warrior persona, and worries about his ability to meet the danger and demands of the Underland prophesies. A cliffhanger ending finds Gregory back in Regalia to spread the news of an imminent rat attack and prepare himself for battle while Queen Luxa heads off to warn the nibblers of the rats’ plans for combat. It will leave readers breathless for the next volume. (Ages 9–14)

It's only a few months since Gregor and Boots returned from the Underland, leaving their mother behind to heal from the plague. Though Gregor's family receives frequent updates on her condition, they all know Gregor must return to fulfill his role as the warrior who is key to the Underlanders' survival. Accompanied by his now-talkative little sister Boots, still considered the honorary "princess," Gregor joins forces with another princess - 12-year-old Luxa - and Ripred the rat to defend the Underlanders and the vulnerable "Nibblers," or mice, from the rat army.