The ん or の, seen here written as なんだ, is explaining something. First, a couple of examples to get these down.
Let's talk about whether or not a book is interesting/funny (an example I'm stealing from Jay Rubin, though I don't have his book with me right now). When would this first question be asked?
おもしろいですか？
Well, you could be at your friend's house, and you see a book on his shelf and point it out to him, and then ask him whether or not it's interesting. In that case, you would say it like the above.
How about おもしろいんですか？
Well, for example, you could be sitting across from your friend. He's reading a book and he suddenly starts to laugh. In this case you would ask him the above, using the ん. Why? Because you're asking for an explanation for his laughter. Something like "Is it (your laughter) because the book is funny?" Of course, it sounds clunky in English.
So, now the sentence ボブは、魚が好きなんだよね.
In this sentence you would be doing two things at once. First, because of the なんだ, you would be explaining something. And because of the よね you would be asserting your explanation and seeking agreement. These are two different things.
For example, you could be talking to a friend and notice Bob at a nearby table, very happily eating some fish. When you and your friend see him, you could say the above statement. The なんだ points out that you're explaining something, in this case his behavior of happily eating the fish. The だよね, on the other hand, asks your friend to also think about it and confirm it. It could be translated as something like "Huh, Bob sure likes fish, doesn't he?" The 'huh' and the 'doesn't he' are a way of conveying よね in English. The 'sure', in this case, is how I'm translating the なん, although 'sure' doesn't always work like this, and there's a million ways to translated なん (sometimes you just wouldn't include it at all in English).
The ん or の, seen here written
The ん or の, seen here written as なんだ, is explaining something. First, a couple of examples to get these down.
Let's talk about whether or not a book is interesting/funny (an example I'm stealing from Jay Rubin, though I don't have his book with me right now). When would this first question be asked?
おもしろいですか？
Well, you could be at your friend's house, and you see a book on his shelf and point it out to him, and then ask him whether or not it's interesting. In that case, you would say it like the above.
How about おもしろいんですか？
Well, for example, you could be sitting across from your friend. He's reading a book and he suddenly starts to laugh. In this case you would ask him the above, using the ん. Why? Because you're asking for an explanation for his laughter. Something like "Is it (your laughter) because the book is funny?" Of course, it sounds clunky in English.
So, now the sentence ボブは、魚が好きなんだよね.
In this sentence you would be doing two things at once. First, because of the なんだ, you would be explaining something. And because of the よね you would be asserting your explanation and seeking agreement. These are two different things.
For example, you could be talking to a friend and notice Bob at a nearby table, very happily eating some fish. When you and your friend see him, you could say the above statement. The なんだ points out that you're explaining something, in this case his behavior of happily eating the fish. The だよね, on the other hand, asks your friend to also think about it and confirm it. It could be translated as something like "Huh, Bob sure likes fish, doesn't he?" The 'huh' and the 'doesn't he' are a way of conveying よね in English. The 'sure', in this case, is how I'm translating the なん, although 'sure' doesn't always work like this, and there's a million ways to translated なん (sometimes you just wouldn't include it at all in English).