Narada Bhakti Sutra is one of the popular Sutras and is attributed to Sage Narad and it expounds the Philosophy of Devotion.
By attaining divine love man becomes perfect, immortal, and satisfied forever.
On attaining true devotion, man does not desire anything else; he grieves no more, is free from hatred and jealousy; he does not take pleasure in the vanities of life; and he loses all eagerness to gain anything for himself. Realizing that, man becomes intoxicated and fascinated, as it were, because he is completely immersed in the enjoyment of the Bliss of the Atman, the truest and highest Self.
Than all other paths, Devotion is readily available and easily attainable.
Narada Bhakti Sutra