The Italian title of a book of Petrarch’s sonnets is "Canzoniere" (literally "Songbook."). The poet worked on it for many years starting in 1336. Its final edition (1373) was entitled in Latin "Rerum vulgarium fragmenta" ("Excerpts in the vernacular"), containing 366 works (317 sonnets, 29 canzone, 9 Sestina, 7 Ballata, Madrigals 4).
The main theme of "Canzoniere" Petrarch set out in the first, introductory sonnet. It is a story of a mature man about confused feelings, that he had undergone a long time ago, in his youth time. The theme of the entire book is love for Laura, high, clean, impetuous, but timid and unrequited. Petrarch hopes his sonnets would meet sympathy and compassion. He hopes to awaken in readers the very same feelings, which he is himself ashamed of now.
Petrarch in his Sonnets is looking at his feelings of love analyzing it from the side, for now, years later, he "is not the same kind of who he used to be." The book tells of the pain of rejected love, unfulfilled hopes, but the passion never spills on the surface. Petrarch is not poured into the overflowing feelings, he reminisces about past love.
Referring to the theme of love, Petrarch followed the traditions of poetry in the vernacular, which, according to Dante, "originally was created for love songs." In "Sonnets" nature is lyrically contrasted to the city, bounding the inner freedom of the poet. The beauty of the woman he loved - that's the beauty of the Renaissance natural world.
Petrarch created in the "Sonnets" special, Renaissance artistic style, which half a century later, had an impact on the entire European Renaissance poetry.