Sir Thomas Wyatt inaugurated the Italian or Petrarchan sonnet into English poetry in Tottel's Miscellany (1557), which also included poems from the Earl of Surrey. He learned of the form during travels in Spain and Italy. While the normal Italian sonnet had two divisions, an octave and a sestet, Wyatt introduced, and Surrey developed, what is called the English or Shakespearean form, three quatrains and a concluding couplet (abab cdcd efef gg) using iambic pentameter (each line has five pairs of stressed and unstressed syllables), a more congenial form for the English language as it offered a fuller range of rhymes.
In 1609 Thomas Thorpe issued 154 sonnets entitled Shake-speares Sonnets: Never Before Imprinted. It would seem that the publication of the sonnets was not authorised by Shakespeare but was managed by Thomas Thorpe, as a result it is unknown if the sonnets are in the correct order or whether all the sonnets he wrote were included, making them almost impossible to date. Some scholars have looked at parallels in ideas and diction with the narrative poems and plays Shakespeare wrote and have suggested that the sonnets would mostly have been written between 1593-1596.
Regardless of this the sonnets seem to be some of Shakespeare's most personal work and are addressed to an unknown young man and a ‘dark lady'. They appear to be divided into two main groups:
The first comprises 1-126 which seem to be addressed to one young man, the poet's much loved and admired friend, his junior in years and superior in social station. Sonnets 1-17, often called the procreation sonnets, are appeals to a young man to marry and circumvent mortality by having children. However in sonnets 18-126 the tone changes even though the poet continues to celebrate the young man as well as the poet's own complete love with more or less related themes, for example sonnets 40-42 seem to reproach the young man for a liaison that has yet to be disclosed, and in sonnets 79-86 it seems that the poet has been displaced for the young man's favour by another, rival, poet. These anomalies have led scholars to debate whether it is the same young man or even a man at all.
In the second group, Sonnets 127-152, there is a distinct change as the poet details his mingled passion and loathing for a dark woman - possibly a forsworn wife – who, having already had the poet as a lover, has drawn the young man into an affair, so that the poet has suffered a double disloyalty.
Concerning the "poetical merits," of Shakespeare's sonnets they received generally the highest praise. In this respect, the remarks of Alexander Dyce in the introduction to his 1832 The Poems of Shakespeare are typical:
Next to the dramas of Shakespeare, they [the Sonnets] are by far the most valuable of his works. They contain such a quality of profound thought as must astonish every reflecting reader; they are adorned by splendid and delicate imagery; they are sublime, pathetic, tender, or sweetly playful; while they delight the ear by their fluency, and their varied harmonies of rhythm. Our language can boast no sonnets altogether worthy of being placed by the side of Shakespeare's, except the few which Milton poured forth,--so severe, and so majestic. (xxxvii)
Time is a continued theme in the poems. 'Mutability', the concern that everything is subject to death and decay, can only be mitigated by the poems themselves. Shakespeare seems in these moments to understand that the poems will live on after his death.