The Atlantic Book of British and American Poetry by Dame Edith Sitwell

This in my opinion is the best anthology of poetry in the English language, and is the one I would recommend to anyone as your first and basic poetry anthology. I could write a long review explaining its virtues, but they will become apparent if you read through the book; here, I will only mention that the selection, which is judiciously balanced between famous standards and neglected gems, virtually teaches you as you read how English language poetry has developed, that many of Dame Edith's introductory remarks include extremely perceptive insights into poetic techniques (and in the case of some later poets, intriguing brief personal comments on them not to be found elsewhere), and that the book is beautifully printed and produced, a joy to read and, like the poems themselves, built to last. That this book is long out of print is an indictment of the value our culture places on poetry. Fortunately, still at this writing available used at not too unreasonable prices. Get it while you can.

[Note:  As this book was first published in 1958, it doesn't include more recent English language poetry, which in my opinion is not much of a loss; I would still highly recommend this book as an anthology covering most of the full history of English language poetry.]