"Bhakti Sutra" says that the love of God is the highest level of love. Narada places bhakti at the top. He considers it better than karma, jnana and yoga, as bhakti is the means as well as the result.
Out of the 84 sutras by sage Narada, the first 24 talk about the nature of devotion. Sutras 25 to 33 explain why the path of devotion is the ultimate. Sutras from 34 to 50 detail the ways to practice bhakti. Sutras from 51 up to 66 speak on the signs of true bhakti. Finally, the last 18 sutras extol those who have reached the highest point of bhakti.