What is Aquinas' response about truth in the book, Introduction to Saint Thomas Aquinas?

Whether God is truth, the short answer is 'Yes'. Whether there is only one truth according to which all things are True, again, the short answer is 'Yes.' Whether created truth is eternal, the short answer is 'not all of the truth is eternal, but all that is eternal is the truth.' Whether truth is immutable, there is truth that is immutable that does not and cannot be change. However, not all truth is of this kind.