In my opinion there too short. I managed to read two of them in a day. But they are brilliant. My favourite was probably the fourth, The Battle of the Labyrinth. The new series is also great so far. My favourite bit in it all is probably when Thalia is flying the bus in Titan's Curse. I also love the mini war between the Apollo and Ares cabins when most of the later cabin were affected by a poetry curse, which I think was in the last one. The film really didn't do it credit.