The Lightning Thief by Rick Riordan is the first book in the Percy Jackson & the Olympians series for "young adults". Even though I do not fall in the aforementioned demographic, I decided to give it a whirl as I've heard mention of this novel on the Interwebz. Well, after a breezy read, my recommendation is to not bother. While it might make for good reading for young adults, I expect that it will fare pretty poorly in the hands of anybody above the age of say, eighteen.
The book is often compared to the Harry Potter series and I can safely say that it comes nowhere near close be it in terms of the imagination or the cohesion of the plot line. The characters also lack definition.