Blake produced the Book of Thel between Songs of Innocence and Songs of Experience. One of the most successful of Blake's illuminated books, Thel contains eight elaborate water-color plates printed in golden brown or green ink. The fifteen known copies of Thel were produced between 1789 and 1818.

As in many of Blake's works, this illustrated poem portrays a confrontation between Innocence and Experience. The heroine Thel is a woman of Innocence who comes to a greater understanding of the underlying purpose of life and of the mystery of death, though the frightening knowledge drives her back to a state of innocence and dread.

Visions of the Daughters of Albion may be seen as a sequel to The Book of Thel, with Oothoon, the woman of Experience, replacing Thel.

In the fifth plate of the book (counting the title page), Thel is shown discovering "the Worm upon its dewy bed," the "Worm" representing "helpless & naked" Youth lying in a Lily of the Valley, representing Infancy.