PFUser *currentuser = [PFUser currentUser];
storeUserID = currentuser[@"connectedBook"]; //Store book id in a string
NSLog(@"%@", storeUserID); // what i get <Book:f4Dg92xC2:(null)>


PFQuery *query = [PFQuery queryWithClassName:@"Book"];
[query getObjectInBackgroundWithId:storeUserID block:^(PFObject *books, NSError *error){
    PFObject *bookObject = books[@"bookName"];
    NSLog(@"bookName:%@", bookObject);
}];