There are several good books that can introduce you to philosophy on a rather serious level.
First, I would recommend a book by Jacques Maritain titled “Introduction to Philosophy” (around $30 on Amazon.com).
I would also recommend Owen Anderson’s “The Clarity of God’s Existence: The Ethics of Belief After the Enlightenment” (around $27 on Amazon.com).
I would also recommend another little book by Josef Pieper called “Leisure: The Basis of Culture” (between $3 and $10 at amazon.com).
If you want additional books let me know.