Java program design question

Question

I'm trying to come up with a simple way of organizing some objects, in terms of what classes to create. Let's say I'm trying to keep track of books. A book can fall under a number of different genres and subgenres. I want to be able to recognize a book as one book and yet have it fall under these different categories. I have a genre class which keeps track of all the subgenres, and a subgenre class which has all of the books in it. I want the book to know all of the genre and subgenres that it falls under. I also want to keep track of some statistics (reviews, comments, number of times read, etc.) based on genre and subgenre and then be able to aggregate them to get numbers for the entire book. In this way, a user could select a book and know, each genre/subgenre that the book belongs to, and soem statistics about that book for each category

What are some ideas for how I can design this?

My thought was to have each Book define a class called BookGroup, and the BookGroup would contain the Genre and Subgenre, along with any relevant information for that category (assuming that subgenres can only belong to one genre). Then in the Book class I would keep a set of bookgroups that the book belongs in. I can add up stats from all the different bookgroups. The only thing I don't like about this is that I feel like a BookGroup should contain Books, not the other way around.

Any other ideas?

Thanks!

Edit: All you guys gave really good tips. I think for simplicity reasons, I might do something like this for now:

class Book
{
     Genre myGenre;
     SubGenre mySubGenre;
     String myTitle;
}

class Library
{
     Map<String,Set<Book>> allBooks = new HashMap<String,Set<Book>>();
     //where allBooks contains a mapping from book title, to all of the book objects which actually represent the same book but may contain different information related to their specific genre/subgenre
}

Answer 1

I'd imagine you would want your classes to look something like this:

public class Book  
{  
String name;  
List<Review> reviews;  
Set<Genre> genres;  
public Book(String name, Set<Genre> genres){}  
}

  public class Genre  
{  
String name;  
Set<Book> books;  
public Genre(String name, Set<Book> books){}  
}  

I am making an assumption here that you will be utilizing a database, in turn you would have a DAO to query on all known books that match a criteria and subsequently perform CRUD operations across the datasets. I feel a bit off by suggesting that the Genre constructor takes a Set of Book objects, but at the moment I can't think of another way to do this right now.