Confused about some OOP concepts... good resources to learn?

(I am sorry if this isn't the right forum for this sort of question, but there doesn't seem to be a "General Programming questions" forum here... feel free to move it or delete as necessary)

Anyways, I have a lot of programming and C# concepts down, but I'm having a devil of a time coming to grasps with object-oriented programming (I've watched the C# Express videos that deal with it, and the VB.NET ones, and the other ones from LearnVisualStudio.net, but still no luck). I understand the concept of objects, and why it's a good idea to encapsulate methods and such in the object (code reuse ). I also understand about properties and methods and fields, and a little about inheritance (haven't really played with that yet). However, where I'm stuck is that I don't understand *why* OOP is beneficial.

For example, if I'm writing an application to keep track of books for a bookstore, I don't understand why it's better to develop a class definition containing what makes up a book (e.g. ISBN, Author, Title, etc.) and then use properties. What I mean is why is it better to put:

class Book
{
private string m_ISBN;
// other fields, etc....

public string ISBN
{
get { return m_ISBN; }
set { m_ISBN = value; }
}

// Etc... rest of Book class
}

Say the application connects to a SQL Server database, using OOP would you assign the ISBN value from, say, a Dataset to m_ISBN, and then in your actual application, set a textbox to the property For example:

txtISBN.Text = myBook.ISBN; // ISBN is set in the Book class

If this *is* correct, then I'm afraid I don't understand *why* you would want to do that instead of setting the DataSource of txtISBN to whatever dataset you use in the program (assume you have a method that creates and returns the filled dataset), say like this:

txtISBN.DataSource = book.BookInfo(); // BookInfo returns a dataset used to populate my textbox

(I realize I didn't put the full code needed to do this; I hope you understand what I'm trying to ask!)

It just seems like an extra step of work (creating/setting the property in the class) and I must not be getting something, because aside from this concept I *do* understand why OOP is better than structured programming.

Since this is a forum for "real" developers and not wannabe dabblers like myself, does anyone know of any good books that explain in-depth the benefits of OOP and why you would want to use it A lot of the examples I see online explain it, but never show any useful examples that demonstrate WHY it's good to use in a commercial application. Any references or resources would be greatly appreciated.

Thank you!