From the early 17th century, the play was famous for its ghost and vivid dramatisation of melancholy and insanity, leading to a procession of mad courtiers and ladies in Jacobean and Caroline drama. Though it remained popular with mass audiences, late 17th-century Restoration critics saw Hamlet as primitive and disapproved of its lack of unity and decorum. This view changed drastically in the 18th century, when critics regarded Hamlet as a hero—a pure, brilliant young man thrust into unfortunate circumstances. By the mid-18th century, however, the advent of Gothic literature brought psychological and mystical readings, returning madness and the Ghost to the forefront. Not until the late 18th century did critics and performers begin to view Hamlet as confusing and inconsistent. Before then, he was either mad, or not; either a hero, or not; with no in-betweens. These developments represented a fundamental change in literary criticism, which came to focus more on character and less on plot. By the 19th century, Romantic critics valued Hamlet for its internal, individual conflict reflecting the strong contemporary emphasis on internal struggles and inner character in general. Then too, critics started to focus on Hamlet's delay as a character trait, rather than a plot device. This focus on character and internal struggle continued into the 20th century, when criticism branched in several directions, discussed in context and interpretation below.
Hamlet departed from contemporary dramatic convention in several ways. For example, in Shakespeare's day, plays were usually expected to follow the advice of Aristotle in his Poetics: that a drama should focus on action, not character. In Hamlet, Shakespeare reverses this so that it is through the soliloquies, not the action, that the audience learns Hamlet's motives and thoughts. The play is full of seeming discontinuities and irregularities of action, except in the "bad" quarto. At one point, as in the Gravedigger scene, Hamlet seems resolved to kill Claudius: in the next scene, however, when Claudius appears, he is suddenly tame. Scholars still debate whether these twists are mistakes or intentional additions to add to the play's themes of confusion and duality. Finally, in a period when most plays ran for two hours or so, the full text of Hamlet—Shakespeare's longest play, with 4,042 lines, totalling 29,551 words—often takes over four hours to deliver. Even today the play is rarely performed in its entirety, and has only once been dramatised on film completely, in Kenneth Branagh's 1996 version. Hamlet also contains a favourite Shakespearean device, a play within the play, a literary device or conceit in which one story is told during the action of another story.
Compared with language in a modern newspaper, magazine or popular novel, Shakespeare's language can strike contemporary readers as complex, elaborate and at times difficult to understand. Remarkably, it still works well enough in the theatre: audiences at the reconstruction of 'Shakespeare's Globe' in London, many of whom have never been to the theatre before, let alone to a play by Shakespeare, seem to have little difficulty grasping the play's action. Much of Hamlet's language is courtly: elaborate, witty discourse, as recommended by Baldassare Castiglione's 1528 etiquette guide, The Courtier. This work specifically advises royal retainers to amuse their masters with inventive language. Osric and Polonius, especially, seem to respect this injunction. Claudius's speech is rich with rhetorical figures—as is Hamlet's and, at times, Ophelia's—while the language of Horatio, the guards, and the gravediggers is simpler. Claudius's high status is reinforced by using the royal first person plural ("we" or "us"), and anaphora mixed with metaphor to resonate with Greek political speeches.
Hamlet is the most skilled of all at rhetoric. He uses highly developed metaphors, stichomythia, and in nine memorable words deploys both anaphora and asyndeton: "to die: to sleep— / To sleep, perchance to dream". In contrast, when occasion demands, he is precise and straightforward, as when he explains his inward emotion to his mother: "But I have that within which passes show, / These but the trappings and the suits of woe". At times, he relies heavily on puns to express his true thoughts while simultaneously concealing them. His "nunnery" remarks to Ophelia are an example of a cruel double meaning as nunnery was Elizabethan slang for brothel. His very first words in the play are a pun; when Claudius addresses him as "my cousin Hamlet, and my son", Hamlet says as an aside: "A little more than kin, and less than kind." An aside is a dramatic device in which a character speaks to the audience. By convention the audience realises that the character's speech is unheard by the other characters on stage. It may be addressed to the audience expressly (in character or out) or represent an unspoken thought.
An unusual rhetorical device, hendiadys, appears in several places in the play. Examples are found in Ophelia's speech at the end of the nunnery scene: "Th'expectancy and rose of the fair state"; "And I, of ladies most deject and wretched". Many scholars have found it odd that Shakespeare would, seemingly arbitrarily, use this rhetorical form throughout the play. One explanation may be that Hamlet was written later in Shakespeare's life, when he was adept at matching rhetorical devices to characters and the plot. Linguist George T. Wright suggests that hendiadys had been used deliberately to heighten the play's sense of duality and dislocation. Pauline Kiernan argues that Shakespeare changed English drama forever in Hamlet because he "showed how a character's language can often be saying several things at once, and contradictory meanings at that, to reflect fragmented thoughts and disturbed feelings." She gives the example of Hamlet's advice to Ophelia, "get thee to a nunnery", which is simultaneously a reference to a place of chastity and a slang term for a brothel, reflecting Hamlet's confused feelings about female sexuality.