It was precisely and carefully written, stating the facts and pulling apart the saintly whitewash Mrs. Gaskell and other previous biographers had done to Charlotte's life. He does a thorough job of getting at the real Charlotte behind all the myth.
I'm not even sure the author liked Charlotte very much, but that didn't stop him depicting her honestly, with the facts that he had before him.
The book ends very abruptly with Charlotte's death. The last few chapters seem a bit hurried, but on the whole it was a good effort.