There are 154 Shakespearean sonnets. They were not written as a coherent narrative but rather as individual poems, and thus, although there are certain themes that recur across several individual sonnets, there is not the sort of thematic unity one would find in a sonnet sequence intended as an organic whole.
The sonnet as a form, especially as developed by Petrarch, was often associated with the theme of love. Shakespeare is no exception to this, and the majority of the sonnets have love as a theme. This theme can be handled in many ways. Some of the sonnets praise the beloved directly and others indirectly. Some suggest that love can bring joy even when the narrator is surrounded by misfortune. Others emphasize that true love endures through age and involves a deep spiritual connection rather than just superficial physical attraction.
The love poems are mainly addressed to a young man but some are also addressed to a woman. They include themes of jealousy, unrequited love, and requited love. Some of the poems also address the nature of time and human mortality.