It could be the theme of exploration. The little green road is like a path leading to the unknown, which is the fairyland.
I haven't read this story specifically, but generally, it might be about an adventure on a little green road leading to a fairyland. It could involve magical creatures, beautiful sceneries, and exciting challenges along the way.
A third possible theme could be transformation. The main character might change as they go through the experiences on the road and in the fairyland. For example, they could become more confident or more in tune with nature.
Sorry, I haven't read this story yet so I can't summarize it.
Another theme could be growth. As the story never ends, the little person is likely to grow and change throughout their adventures. They might learn new skills, gain wisdom, and develop as a character. This growth could be both physical and mental, as they encounter different situations and people.
Maybe it's about the growth and development of young golfers. They could be the 'little aces'.
It could be friendship. Two little monsters might be going through various situations together and learning the importance of being friends.
Love could be the main theme, as it's in the title of the story.
One possible theme might be love. The green dress could be a symbol related to her love interest. For example, she might meet someone special while wearing the green dress, and the story could explore the development of their relationship and how it affects her. Another theme could be transformation. The woman may change in some way throughout the story, and the green dress could be a marker of that change, either literally or symbolically.
The theme could be discovery. Since it's about a book, Lucy might be discovering new things through it.
One possible theme could be the blurring of the lines between the divine and the mortal. With 'little g gods', it might be about how these semi - divine beings are not so different from us.