This anthology is, for my money, the best introduction to poetry around at the moment. Having started in the London Underground, it reflects the cosmopolitan makeup of that city. There's something from almost every corner of the world here - the Caribbean, medieval Ireland, several poems in translation... plus excellent (and sometimes very humorous) notes on the poems. There are classics too, such as the famous poem by Auden used in Four Weddings and a Funeral (the original title is simply "Song".)
If you'd like to own a very good, accessible poetry anthology but you're frightened by the size of, say, the Norton anthology, buy this one instead.