Reviewed by Marguerite Pigeon Dementia might seem like the anti-muse: not creative inspiration, but its sapping. Yet, in her new collection, Cold Metal Stairs, Su Croll follows dementia—her father’s—as it pulls her vicariously, clanging and spiralling downwards, through grief, fragmentation, and fear. The poems in this collection enact the repetitive, temporally confusing stretch during which…