The Power of Friendship
Friendship is probably the most important theme in this book. Although all of the characters face dire and seemingly impossible challenges, they all rely on friendship to guide them through. Percy is strong and smart, but it's his relationships with his friends, particularly Grover, Annabeth, and Tyson, that allow him, and the larger community of the camp, to succeed in this novel. In the midst of uncertainty, danger, and fear, each character finds their way through their friendships, which often are more like family bonds. For Percy, his friendship with Annabeth leads to their ability to find the Fleece; his friendship with Grover allows Grover to form an empathy bond so Percy can figure out where he is. Annabeth's loyalty to Percy is influenced by her earlier friendship with Luke and Thalia, even though that friendship didn't end well. Tyson's ability to make friends gets the group out of more than one snare, and as the novel progresses, we see over and over how friendship can make even the darkest times seem brighter.
The Complicated Nature of Good vs. Evil
Despite the fact that there's a clear protagonist and antagonist in this book, the difference between the right and wrong sides is still very complex. Luke is in the wrong, but he still makes some good arguments, and his background helps us to understand why he acts the way he does. It's true that the gods are cruel, and that they don't take good enough care of their children. It's also true that the West has done some awful things, and that there are still things about Western Civilization that need to change. The problem is that Kronos isn't concerned with changing things, he's concerned with destroying them. So while Percy sees the points that Kronos is making, he knows that it's not the right side to choose. At the same time, Percy is also mindful of the fact that the gods also have to change. Fighting for them doesn't mean they've done no wrong. Mr. D is still mean to campers, and Zeus will still kill Percy if he gets on a plane. In the coming war, the gods will have to deal with their own wrongs as well as those of Kronos.
Family
The complicated nature of family is a key theme in Sea of Monsters. Throughout, we see how the conflict between the gods and their children stems mostly from parental neglect. Luke turns evil because of Hermes's abandonment of him, Percy's own personal struggles are centered around his difficulty accepting Tyson as a brother, and even Kronos takes revenge against his children, who trapped him in Tartarus after the first Titan War. At its heart, the coming war with Kronos is a huge family drama. Everything is caught up in very personal relationships. Even as Luke talks about how he's on Kronos's side because his family betrayed him, he has also betrayed his own family by trying to poison Percy last summer and poisoning Thalia's tree this summer. Despite Kronos claiming to be in the right, it's his side that ends up coming between families, especially as the war gets progressively worse.
Kindness
Sea of Monsters explores the enormous impact that kindness can have, both on the person showing it and the person to whom it is being shown. The kindness of Percy and Tyson in particular drive much of this book, and the quest for the Fleece would have failed without the kind gestures that they make toward other people. The quest is only begun in the first place because Grover knows Percy well enough to know that he's a kind friend who will follow him to the ends of the earth, and it is Percy's kindness to Tyson that makes it possible for him to be such a valuable part of the team. Kindness proves to be the most effective response every time and provides the bedrock for the friendships that save Percy throughout the book. This is in sharp contrast to Kronos's behavior, whose response to the gods is to try to get revenge for the wrongs that have been done to them. Ultimately that lack of kindness, proven by Kronos's desire to destroy everything, is what prevents Percy and Annabeth from joining forces with Kronos.
Pride
Pride is something that multiple characters struggle with in this book, often leading to the obstruction of their goals. Clarisse, for example, is prideful to the point where she puts others in danger, while Luke's pride allows Percy and Annabeth to evade his plans. Even Percy and Annabeth's pride is manipulated by Circe, who makes them feel self-conscious in order to take advantage of them. Overall, pride prevents characters from seeing what's right in front of them. It's the humble characters, like Tyson, who are best able to interpret situations correctly, and who often end up saving everyone else in the process. While confidence is important, and the characters grow in confidence throughout the novel, pride is something that they have to face down and conquer. As the series continues, we'll see how each character grows into their own strengths without overestimating their abilities.
Cleverness
In a book that references the Odyssey so thoroughly, it's not a surprise that cleverness is a big part of how the characters overcome obstacles. From the very beginning of the book, where Percy must figure out how to outwit the giants, to the climactic fight with Polyphemus, the characters must rely on brains instead of brawn. As teenagers, they can't defeat monsters with physical strength, so they have to find other ways. As the book progresses, Percy and his friends use a variety of tactics to take advantage of the strengths that they do possess. Kronos outsmarting them at the end only proves how important it is that the demigods build skills of strategy as well as strength. Each of the characters has their own sort of intelligence that they use differently. Annabeth, like her mom, is a great strategist, while Percy is good at coming up with unexpected solutions to the problems in front of them. Tyson is good with machines, and Grover is good at finding things—together, they form a team that's even smarter than the sum of its parts.
Safe Havens
Being a demigod is dangerous, and while Percy is obviously fighting for what's right, one of, if not the, most important things to him is safety. He is invested in securing the safety of his friends, whether that's searching for Grover or looking for a way to heal Thalia's tree for the camp. As a hero, Percy isn't particularly invested in attaining glory or defeating a huge evil, although those are things that come along with the journey he'll have to take. Rather, Percy fights so that the people he loves can have safe havens, where they don't have to worry about being attacked. In the real world, Percy is either being attacked by monsters or struggling in school. For a long time, spending time with his mom and with Grover were the only times he felt safe. Now that those havens have expanded, Percy is determined to keep them safe.
