Answer:
Step-by-step explanation:
adjective clause: that I told you about.
word modified: novel
An adjective is a word that modifies a noun. Usually it is quite clear. For example The red text is a math book.
red is an adjective
So is math believe it or not.
In this case, you cannot strip the clause down to make it look like an adjective, but it nevertheless is. It modifies makes the book special because I told you about it.