Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Bitter, Hopeful, Ambiguous
Bitter
Woman on the Edge of Time is a bitter, bleak book. Marge Piercy looks around at her own time and spits on it. Connie is desperate, beaten, and sad—and no one cares:
Only one person to love. Just one little corner of loving of my own. For that love I'd have borne it all and I'd never have fought back. I would have obeyed. I would have agreed that I'm sick, that I'm sick to be poor and sick to be sick and sick to be hungry and sick to be lonely and sick to be robbed and used. (19.78)
Connie is miserable, and the book shows you, carefully, brutally, why she has every right to be. Spoiler: this is not a cheerful book.
Hopeful
But! At the same time, the tone of much of the book is hopeful. The future looks like a great place. When Connie "assents with all her soul to Angelina in Mattapoisett" (7.120), it seems like it's the author assenting, too. Mattapoisett, without hunger or hatred, is a lovely place, and Piercy seems to think we can get there from here. That's cheery, right?
Bitter and Hopeful? We're Confused.
So how do you reconcile that attitude of bitterness with that attitude of hope? Well, you don't, really. That's why the novel is tricksier than a hobbit.
Does Connie ensure the future of Mattapoisett (yay!) or does she destroy that future (boo!)? You never find out; it's not clear whether the novel sees Connie as heroic or benighted, unusually clear-eyed or horribly confused. The last line—"There were one hundred thirteen more pages. They all followed Connie back to Rockover"— is clinical, like the medical records themselves, and abrupt. You don't know what the novel thinks about Connie at the end there. You're left to make up your own mind.