The contents (of this class) make you think a lot about the subject and at the same time very interesting.
In my opinion the contents are truly thought provoking and interesting as well.
内容が深いというのは、英語で以下のような表現を私が使っております:
I think the topics chosen today are very thoughtful and interesting-今日決められた内容が深くて面白いよね。
The teacher gave today a very thoughtful lecture and I must say it was extremely interesting-今日の先生の講義の内容は意味深くて皆の注目をあびたと思う。
His new work left a thoughtful impression on the minds of readers-彼の新作品が読者にとって意味の深い印象をきっと残ったじゃなかいなな
以上の言い方を私がよく使っております。
どうぞご参考までに。