Who has the first book in gravity falls?

I think its the uncle cause in the creits when it ends the primid says the uncle is not what he seems.that means he not human if he was it would uncle is not who he seems.and in the theme song when they show the trees look at the right part and u see a back thing running its looks like big foot that the uncle he is cause in the 1 episode he goes in his lab thats i know to find more at the end of each episode it said hfdbugvv u take the letter of each and in abc go back 3 letters