THE LONG APPROACH by Maxine Kumin (Viking: $14.95). It's difficult for poets to know when they're at their best. Maxine Kumin could have used some clear-eyed editorial help with this book, which contains too many flawed poems in what might have been a fine, strong collection. The poems of the first two sections often accumulate interesting detail but slip into cleverness or ramble, rather than being incisive statements. Last lines remain strained attempts at summarization, not organic fulfillments. Kumin writes about family memories, then of world issues--painful religious and political conflicts--but doesn't arrive at her best work until, in the final section, she arrives at her farm in New Hampshire. Here, she's at home. The writing is thorough, well-wrought, insightful. Fascinated by the interplay of life and death, destruction and hope, she finds her truest images in seasonal cycles, in animals, gardens and weather. Larger concerns of world conflict emerge within a context that sets natural possibilities in place, so that if there's tension, there's also balance. She says, of a bear, " . . . Something we watched, touched, and let be." When Kumin watches calmly and allows nature to guide her, then the poetry is real and whole.