This is probably my FAVORITE book of the series, with the 4th one! :D 
 This book builds up on the first two books incredibly well! You meet so many new gods, new characters, and the plot really builds up to the final prophecy! 
 In this book, we meet Apollo and Artemis, two of my favorite gods. They're twins, and they're just so different, and both so helpful! Artemis's hunters are so cool, and they are a really good addition to the story :) Apollo is such a cool guy/god, who's really helpful to the quest group! Plus, he's hilarious, and apparently good-looking. He's probably my favorite of the olympians :) 
 "Green grass breaks through snow, 
 Artemis pleads for my help, 
 I am so cool" 
 Oh Apollo... the haikus are... uh.. a good try! 
 We also meet Aphrodite, who seems supper giddy and happy, EXACTLY what you would expect from the goddess of love! 
 We also get a bit more Zeus-ness. Thalia, being the daughter of Zeus, manages to get his attention and have him help out while they're at Hoover Dam, which was really cool. 
 About the Hoover Dam scene, can we just talk about how legendary that scene is? It became so popular, and is now EVERYWHERE! I went to Hoover Dam this summer and couldn't help but start laughing to myself. The meme is now huge, and it's totally understandable why! 
 ""Let us find the dam snack bar," Zoe said. "We should eat while we can." 
 Grover cracked a smile. "The dam snack bar?" 
 Zoe blinked. "Yes. What is funny?" 
 "Nothing," Grover said, trying to keep a straight face. "I could use some dam french fries." 
 Even Thalia smiled at that. "And I need to use the dam restroom." 
 ... 
 I started cracking up, and Thalia and Grover joined in, while Zoe just looked at me. "I do not understand." 
 "I want to use the dam water fountain," Grover said. 
 "And..." Thalia tried to catch her breath. "I want to buy a dam t-shirt." 
 I busted up, and I probably would have kept laughing all day, but then I heard a noise: 
 "Moooo."" 
 SO CLASSIC! 
 We also get lots of new mythology in this! We start getting some more hints about the Titans, Atlas, the Ophiotaurus, the Hesperides (I spelt that right on the first try, can't believe it o_o ) some of the gods, and Pan. 
 It's so cool that Grover's personal life goal really expands in this book. We understand it on a deeper level. Even though it turns him into a passed-out goat. 
 We also get to know Annabeth's family situation more, even though she is missing throughout most of the book. This really helps understand her better. 
 Percy is a great as ever, and, as in the last book, we can tell that he matured a bit! 
 Thalia was cool but annoying. I'm not sure I like her as a person, but as a character, she's a great addition. There were a few scenes where she was... aggravating. But it was necessary for the book, so it's okay :) 
 Blackjack is so cool and sassy and so awesome!! 
 And of course, in this book we meet Nico and Bianca. I'm so sad about Bianca, though! But she was too nervous of a character, anyway. But Nico has grown to be one of my favorite characters in the series. (If you read the Heroes of Olympus, his character grows SO MUCH it's incredible!) 
 The pace is so great, and again, Rick Riordan really manages to piece everything that he introduces in this first two books together in such a great way! The book is so hilarious, it's hard not to smile like an idiot while reading it! 
 AND. THE. END. FIGHT. SCENE. IS. AWESOME! 
 Also, the foreshadowing is so absolutely incredible in this installment! I won't say much, but some characters that seem unimportant become important. Some one-liners in the book end up being super important, and some small events and things that can be over-read get magnified in the last book. Very sneaky, uncle Rick ^-^