I'd give this the same five stars I would give to the Arden edition, but for very different reasons: while Arden contains within its rather porky volumes all the immediate reference to a Shakespeare play one could possibly decide to desire, Oxford knows how to do introductions that actually do that - introduce.
You need no degree in literature, no knowledge of technical jargon, no previous experience of the play in question: the gentle, hand-in-hand editors of Oxford will reveal all (that is possible to reveal in an introduction half the length of those of Arden), grecefully and comprehensively.
So buy this to start with (especially this particular new print, which is printed on better paper, with better ink and has a nicer cover than the last one); and if you find yourself interested, intrigued, and want to know more - invest in the porkier Arden.
As for the "Merchant" itself - long story short, it tells the tale of a Venetian Jew's quest for justice or revenge, you decide:
Antonio, a wealthy merchant down on his luck, borrows money from him on behalf of his friend Bassanio, who needs it to woo a lady. Shylock the Jew, hating all Christians because they all hate him, draws up a contract stating that, should Antonio be unable to repay him, he would do so by means of a pound of flesh rather than money. When Antonio's precious cargo is lost at sea, Shylock turns to the authorities to claim what is his: Antonio's heart, to be cut out there and then. There follows the most exciting, nail-biting trial scene in the history of drama, so I will not spoil the ending.
A very complex play (critics have yet to agree whether Shylock is a bloodthirsty villain or a persecuted hero), very much still relevant with its central theme of religious intolerance, this deserves to be read. Then when you can, go see it at the theatre: that's the way Shakespeare is meant to be enjoyed.