Final answer:
The subject of the sentence "Me interesan los libros" is the books (los libros).
Step-by-step explanation:
The subject of the sentence "Me interesan los libros" is the books (los libros). In Spanish, the verb "interesar" is used to express interest or liking for something. It is a reflexive verb that agrees with the subject. In this sentence, the subject is implied and it is the books.
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