This is definitely the book that divides most Hughes readers. For some it's the peak of his achievement in the mythopoeic vein - and the range of cultural reference is amazing. Hughes aplcalyptic mishmash of 'scripture and physics' plunders from theology, anthropology, science, myth and popular culture with both verve and intelligence. For others, however, the writing is criticised as sloppy, hit and miss - and certainly, if you were brought up to appreciate the 'finished', constructed poems of the 'practical criticism' era, then the shock to sensibility must've been immense.
A lot is still said about the 'blood and guts' Hughes, and 'Crow' might well be one of the more 'violent' of his books. But even here there are poems of real tenderness and concentrated awareness. If you don't believe me, check out 'Little Blood' and especially the beautiful, 'Undersong'. 'Crow' might well boil down to a book essentially about the struggle to survive in a destructive universe, but it is also haunted and undercut by possibilities that are more vulnerable, fecund and creative. This has always been the side of Hughes that prevents him from lapsing entirely into nihilism, and even in this, perhaps his darkest book, there is something to scavenge from the rubble.
Wherever you stand, though, there's nothing like it anywhere else in British poetry.