One of its most famous readers was William Shakespeare, who seems to have borrowed the Proteus-Julia-Sylvia plot of The Two Gentlemen of Verona from Felismena's tale in the Diana.
Among these is a warrior maiden named Felismena (not truly a shepherd, but dressed as one for the time being), who rescues Sireno and his friends from an attack by wild men.
In the fourth book they are welcomed by Felicia at her castle, and proceed to tour the wonders within (including the halls of Venus and Mars, and a performance by the legendary Orpheus).
Felismena finds her lover, Don Felis (or "Felix" in the English translation), and rescues him from an attack by enemy knights.
Scholars now believe the new material to be Montemayor's own work, though the decision to add them to his pastoral romance may have been made by an enterprising publisher.
[2] While inspired by Jacobo Sannazaro's Arcadia, Montemayor's Diana is arguably the first major work of pastoral prose fiction in the Renaissance, placing just as much emphasis on its ongoing plot and interwoven stories as on the poems sung by its shepherd protagonists.
Speaking more broadly, Geoffrey Bullough, Judith Kennedy, and Stuart Gillespie have all noted that Montemayor's pastoral romance seems to have been foundational for the development of Shakespeare's comedies: they point particularly to Montemayor's influential exploration of love, his emphasis on strong female heroines and their perspectives, and his treatment of amorous intrigue and entanglements.
[...] To begin with Montemayor's Diana, I am of the opinion that it should not be burned, but that everything having to do with the wise Felicia and the enchanted water, and almost all the long verses, should be excised, and let it happily keep all the prose and the honor of being the first of such books.