There are many parallels between the "Book of the Keys of the Work" and "The Book of Pictures“ in terms of subject and style: Both books are written "to my lady" and mainly "in dialogue form, [... have] the same emphasis on the fact that there is just one alchemical operation [...], the alchemical work is one and emphasises the same central role for Democritus, 'the head of the sages of his time' [...]. The operation in both books centres on a composition of vapours [...]. It has the same essential feature of extracting the subtle with 'gentleness' [...] from all four natures, the mixture of like with like, and the need to bind the fugitive spirit. They have analogies in common, for example that of copper with the human being.