The two main characteristics of this excellent play that you need to know about are its black humour and the way it is an example of the Theatre of the Absurd. This latter term relates to the despairing vision of the human condition in life and also the style that is the vehicle that is used to give voice to that vision. The principal concept of this play and of other works that are examples of the Theatre of the Absurd is that human life is essentially meaningless and without purpose and that we live in a universe that is profoundly indifferent or even hostile to us.
Apparently in contradiction to this unyielding and thoroughly depressing view of life and man's place in it is the intensely comic nature of this play. If you look at the subtitle, for example, you will see that Beckett entitled this play "a tragi-comedy in two acts," and many critics have written at great length about the way in which the play manages to maintain a precarious and delicate balance between tragedy and comedy. The comedy element is appealed to through the numerous elements of slapstick comedy and humour, such as the wild hat-swapping scene in Act II and the various examples of humorous dialogue between the two central characters. The black comedy can be linked in to our understanding of the Theatre of the Absurd and how this impacts our understanding of the play. After all, if we really do live in a universe that is profoundly indifferent to us, if not hostile, the least we can do is laugh at it.