I liked it, although not as much as I liked The Titan's Curse. It was still better than the 1st two books in the series. 
 The Battle Of The Labyrinth is about Percy and friends as they navigate the legendary labyrinth in order to prevent Luke (a former friend turned traitor) from invading Camp Half-Blood. 
 Like with the other books, I loved the mythology element of this book, and liked how the labyrinth was so central to the plot. I also really liked the plot, and it was full of action and adventures. 
 There are a couple things that are rapidly becoming very annoying. One, Percy's inability to stay in one school for more than a year. At first, it was okay, but now it's just annoying. Why not just home-school him or keep him at Camp Half-Blood year-round at this point? Why keep sending to different schools every year? 
 Two, Percy doesn't seem to be growing as a person. I honestly don't see much change between Percy in the first book, and Percy at the end of this book. It may be because Percy is the one narrating the series, but there should be some differences between 12-year-old Percy and 15-year-old Percy, and sadly, he still seems to be the same. 
 It gets a 3 out of 5 because there are a couple things that are getting old (and things are starting to get slightly repetitive) but the mythology element is really interesting and the plot was really fast-paced.