The Garuda Purana is one of the eighteen principal Puranas, as stated in the Shrimad-Bhagavatam (SB 12.7.23-24): The eighteen major Puranas are the Brahma, Padma, Visnu, Siva, Linga, Garuda, Narada, Bhagavata, Agni, Skanda, Bhavisya, Brahma-vaivarta, Markandeya, Vamana, Varaha, Matsya, Kurma and Brahmanda Puranas. The Garuda Purana has nineteen thousand slokas.
In a Bhagavad-gita lecture given in Los Angeles on February 15, 1969, Shrila Prabhupada said, "There are eighteen Puranas. Men are conducted in three qualities: the modes of goodness, modes of Passion, and modes of ignorance. To reclaim all these conditioned souls in different varieties of life, there are presentation of the Puranas. Six Puranas are meant for the person who is in the modes of goodness. And six Puranas are meant for the persons who are in the modes of passion. And six Puranas are for those who are in the modes of ignorance."
The Garuda Purana confirms that it is one of the six Puranas that are meant for persons in the mode of goodness. It says that the Bhagavata Purana is the foremost, the Visnu Purana is Next, and the Garuda Purana is third in importance.