BOOK MARKS

A SLENDER THREAD, by Diane Ackerman (Random House. $24). Diane Ackerman is a sort of hippie naturalist, and this is her latest excuse to chase butterflies. The book is ostensibly about Ackerman's work manning a crisis hot line. Still, you've got to wonder what suicidal callers would make of her fuzzy, planet-hugging effusions, reports on the revivifying effects of bicycling and endless chatter about the squirrels in her backyard. (Circle of life: yeah, we know.) Ackerman declines to discuss her own emotional résumé, but does say airily, "I was bom with a poet's sensibility, and Prozac made it impossible for me to do what comes naturally—think metaphorically, allusively, exploring the hidden connection between seemingly unrelated things."