I have read Harry Potter and the Philosophers Stone and am really impressed with it.
As we know that the series was first intended to be a childrens series, hence many adults might find it under them to read it, but, this story indeed had the potential to appeal to all adults, teenagers and children alike.
It follows the adventures of Harry Potter, an 11 year old boy who never asked for the thrills and twists that he gets.
As far as the issue of readability goes, I think it is an easy read for those who have atleast some amount of experience of the genre.
The character developement by J.K Rowling is in itself a masterpiece and the world building is extraordinary.
Also, the hints to the secrets of the end of the series start right here in this book ( so you might wanna read it seriously ; ) ) .
This book carries the potential to stimulate your inquisitiveness, and at the same time make you plunge deep within itself.
The character of Harry is quite relatable, who possesses all the qualities a normal human has ( ignoring the fact that he is a wizard. oops, well, thats hardly a spoiler) .
So if at last you have made up your mind to dive deep into the Harry Potter series, then dont hesitate, but know that you are in for more than just mere surprises!
My Regards.