The Sea of Monsters (Percy Jackson and the Olympians #2)
by Rick Riordan
Wow! The second book in the series is even better than the first book! I think it's because we were already introduced to the characters and world so there was no need to explain and so the story just jumped right in.
A very good sequel. I loved Percy and Tyson's relationship (not going to lie, I cried during a part in this book). :) The Percy Jackson series is fun. I'll be reading the next book.