Answer:
To me,the Percy Jackson series was very readable and fun. I loved reading from Percy's perspective,how humorous he was,etc. It is true that Rick Riordan's writing style is very simple but after all,he is an author for younger readers and does seem to have succeeded in getting reluctant readers to read.
His characters are very memorable and you tend to just like them immediately. Even the ones you don't like,you'll eventually find tolerable. It's also a plus that I happen to love Greek mythology. Rick Riordan at least manages to present all the elements of Greek mythology quite accurately. Even though it is a kids' book,it still manages to be deep and dark at the right times so it can appeal to older readers as well.
I started reading the books at 13 and loved them. I'm not too fond of the Heroes of Olympus,however. It has lost the Percy Jackson charm in my opinion.
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