I read the e-version and it had some glaring typo and grammar mistakes....but that isn't enough to put me off a book if it's fast paced and contains a balanced mix of realism and fantasy, and a refreshing lack of vampires, zombies and other blood-thirsty examples of the nether world. 
 Rick Riordan certainly scores with weaving Greek mythology into the present-day US, and as a means of introducing Greek gods to reluctant students, this is as good a means as any. 
 What I didn't like was the ADHD aspect to Percy's personality - the symptoms described didn't seem to match personal experiences of the condition and there was a tick-box mentality towards cataloguing the known or possibly attributable characteristics of ADHD from which Percy suffers. The flip-side to that is that Percy's ADHD 'weaknesses' are turned into positives in Riordan's take on the making of a god, and given all the uncomfortable press ADHD receives, this has to be a plus for any kid who has been labelled ADHD/Asperge's Syndrome/Autism Spectrum. 
 For an average 12 year old suffering with ADHD, Percy comes across as being far more perceptive than is possible, able to vanquish his foes without any basis other than being hyperactive and therefore possessing super-fast reflexes. Annabeth seems much older and is set up from their first meeting as a love interest, regardless of her crush on the older, more accomplished Luke. Luke is nicely foreshadowed at the beginning of the book, but Mr D is a little tedious by the end. The description of the Furies is a nice twist, as is the modernisation of Olympus and the reasoning behind its present location. 
 It's an easy, fast read for the age group at which it's aimed, and despite being an HP copycat, Percy Jackson brings a slew of different characters and adventures to fill some of the breach left with the vanquishing of Voldy. It won't provide the same emotional intensity as HP, but it's a fun-filled way to catch up on some ancient Greek in an American setting.