Celan becomes indispensable to most who read him. If you’ve not, yet, then Hamburger’s Selected Poems is maybe the most useful place to start — more copious than any other single book I’ve seen in English, and printed bilingually in the practical way (Deutsch and English pages facing each other)–the better for us Hochschule Germanists to crib from.
Oddly, Celan backed away from Death Fugue as it became popularish. He found it – as I understand him – to be too theatrical, or maybe just too obvious, in its refraction of “Deutschland”. I think he wrote poetry differently – more fractured, more piercing and monstrous, (to me) better – in reaction to the fairly rapid approval of Death Fugue.