Nicholas Manning made some interesting points about Paul Celan and interpretation (with three beautiful photos of Celan, one with his wife Giselle). My comments:
1) The worst thing you can do when teaching Celan is what Gerhard Sauder did on the first day of an otherwise wonderful Celan seminar I sat in on in Saarbrücken years ago: "Es freut mich, dass so viele gekommen sind, um diesen schwierigen Lyriker mit mir zu lesen." Once you declare Celan difficult, you've closed off the students to direct access to the poems' beauty. Perhaps I say this because when I first read Celan in a "Literature of the Holocaust" course with John Felstiner, John did not say anything about difficulty, and I read Celan, and the stunning effect of the poems was utterly clear. In terms of reference, the poems had opacities, of course; but as I was able to get right to them as works of art.
2) I find that Celan can be read using careful close-reading techniques as long as my starting point is that I take things literally. The poems may not be referential in the sense of describing realistic scenes, but they do describe scenes.