North is Seamus Heaney's fourth book of poems. Death of a Naturalist was his first, a fully achieved book, followed by a second volume—so often observed in young poets—which was hasty and inferior, Door into Dark; followed in Heaney's case by an excellent third volume, Wintering Out, and now by North which is the best of all. One has the sense in Heaney that politics is forced upon him by the combination of nationality and circumstance…. Circumstance invades this volume…. The second and final section of this book [is politically inspired]. It is good poetry—and there is not a single poem among them that ranks with Heaney's best. It's a poetry written out of social necessity. No man or woman in Northern Ireland at this time could avoid social statement without loss of humanity.

But when mad Ireland teases Heaney into the truest poetry, in...