Ostensibly a biography of Emily Brontë, A Chainless Soul quite naturally contains a great deal of sister Charlotte. Emily, the author of Wuthering Heights, makes for a remarkably difficult subject. She was dismal and friendless. She wrote some earnest poetry, one extraordinary novel, and a few unremarkable letters. She died just when her story was getting interesting. Charlotte, of course, lived and wrote longer than her younger sister, and she was not above pleasing publishers and biographers. As a result, most of what we know about Emily comes through what Katherine Frank calls ''the refracting and sometimes distorting lens of Charlotte Brontë's vision.''
A Chainless Soul is a sobering portrait of Emily as, among other things, an anorexic whose last hunger strike killed her. Still, Frank writes with a healthy measure of awe. Emily never fell in love, Frank reminds us, but she managed to write ''the most cataclysmic love story in the English language.'' B+