The devotional poets of the 17th century were men like John Donne and George Herbert. Like most poetry during this time period, these men wrote lyrics, which were often short and not necessarily narrative in nature, but full of expression, emotion, and religious conviction.
Devotional poetry (even today) is considered meditative in nature. It reflects the poet's spiritual passions and religious convictions, and attempts to persuade the reader to feel similar feelings. In the 17th century, much of this poetry was a turning away from the "church" (most likely the Catholic church) but a turning toward a closer intimacy with God. It was very personal, it was very introspective, and it often reflected on natural beauties in the world (which would point to God).
Additionally, 17th century devotional poetry can often be read as love poetry. In much of it, God is not mentioned nor specifically named. Therefore, the devotion is to an unnamed something. Purposefully ambiguous, this kind of poetry is adaptable and applicable to several situations, rather than be limited to a "religious" box.