Answer:
Indirect object.
Step-by-step explanation:
A noun phrase is quite simply put, a phrase that contains a noun with a modifier. It functions as a noun but along with the modifier.
In a sentence, the subject is the noun doing the verb and the direct object is the receiver of the verb. An indirect object is one that receives the direct object.
Therefore, in the given sentence,
I (subject) made sure to bring (verb) my favorite book (indirect object) to camp with me (direct object).
Thus, the noun phrase "my favorite book" functions as an indirect object in the given sentence.