The mood of The Mill on the Floss is closely linked to Maggie’s moods, and, over the course of the novel, she experiences a wide range of emotions (joy, sadness, fear, shame, romantic desire, and more). That said, even as Maggie occasionally experiences positive emotions, the mood of the novel always has something of an oppressive and bleak charge. This is due to the fact that, as Maggie matures from an open-hearted and carefree child to an adult, she discovers all of the social pressures on her as a woman in a conservative community.
About halfway through the novel, in a moment of direct address to the readers, the narrator even comments on the “oppressive” mood of the story:
I share with you this sense of oppressive narrowness; but it is necessary that we should feel it, if we are to understand how it acted on the lives of Tom and Maggie—how it has acted on young natures in many generations, that in the outward tendency of human things have risen above the mental level of the generation before them, to which they have been nevertheless tied by the strongest fibers of their hearts.
Here the narrator says that it is “necessary” for the mood of the novel to be bleak as it captures something important about the reality of stifling provincial communities where young people are expected to follow the conservative rules of their elders from previous generations.
Also affecting the mood of the novel is the fact that when Maggie feels love for someone, she simultaneously feels trapped. For example, Tom never loves her in the same intense way she loves him, judging her harshly for her mistakes and ultimately rejecting her entirely after she runs away with Stephen. In her relationship with Philip, Maggie knows that Tom would not approve of her being with him, so she feels torn even as she also enjoys Philip’s company. And finally, with Stephen, Maggie knows that no one in the whole town approves of her being with him, so she never lets herself fully feel her love for him. Readers are with Maggie through all of these ups and downs, leading to an ambivalent, conflicted mood.