The original "Percy Jackson and the Olympians" series is five novels plus a few short stories.  (The first one was printed in 2005.)  The sequel series, "The Heroes of Olympus," has just the one book (<span class="bbc_u">The Lost Hero</span>) so far.<br/><br/>Try your local library, there's a good chance they'll have these.  (I can't even remember how I stumbled onto them.)