The greatest compliment one can pay a volume of poetry is that it excites. It doesn't altogether matter whether that excitement is the arousal brought by Dylan Thomas's energies or the mind-knotting orchestrations of Geoffrey Hill; nor does it matter if it is that engagement of the critical and analytical, tangled with pleasure and trepidation, which O'Neill accomplishes in us. Gangs of Shadow is an exciting and most rewarding volume, less menaced than its title might suggest, and more celebratory of that accumulation of black type, those gangs of poems, which we come away feeling are certainly on our side.