An interesting beginning, but lacking a few key peices to let us understand it clearly. For example, we have no idea how old Harry is when he gets the book. We don't know how far back in his ancestry this John potter is. It's also hard to imagin that a book hand written in ink would not be blurring in the rain you describe happening.
Just a few thoughts to make it less vague and more realistic.
Author's response
Thanks for the review! It's always nice to have people give their opinion about my work - I find it helps me to construct better chapters.
Most of these attributes you addressed will be covered in the next chapter, if you're patient about it. The others don't, in my humble opinion, matter overly much. John Potter is more of a flat character - he won't be mentioned hardly at all after this point. As for the book not blurring in the rain... Well, it's magical, and been charmed to survive for hundreds of years, so a little rain won't hurt it.
Thanks again for the review!
~Grimaud