How reliable is the narrator in the good soldier by Ford Madox Ford?

I don't think that the narrator is very reliable because he is so embroiled in the events that take place. The story is narrated by the American husband and is in some sense a detective story, but he is no investigator. The facts come to him unwillingly, since he would have preferred from the beginning not to know; the suspense depends not on what has happened, as dramatic as it turns out to be, but on the narrator's unfolding interpretation of the passionate emotions manifested in very small gestures or brief remarks.

Ford's greatest gamble is in the naïveté of the narrator (Dowell), supposedly an idle but well-meaning wealthy man from an old Philadelphia family who readily accepts a sexless marriage with a woman (Florence) whose emotional life is a secret and a deception. I don't have the novel with me but I thought this excerpt might help.