There are quite a few possible themes for this novel; Huxley has some very potent points to make in this dystopian story. One theme is that of happiness, and the ideas behind how to achieve it. Happiness, complete and total, is the focus of their society, because a happy people is a producing people, and that means success for their society. They think that happiness is created through engineering people to think, act, and actually genetically reflect certain beliefs and attitudes. They specifically engineer people's bodies to be content with their station in life, with no rebellion or independent thought. They also assert happiness comes from a lack of family ties--mother in their society is a bad word. Instead, children are raised in groups. As Mond explains at the end of the novel, family ties creates drama, passion, love and intensity, all which can be tied to heartache, despair and pain. Get rid of families, get rid of the bad stuff. Happiness is also created through soma, a drug that takes people away to happy places; another release for them is through uncommitted sex with multiple partners. Keep the people happy through physical sensations--this helps them to release pent-up tension and any violence they might feel.
Another theme of this novel is that of agency, or the ability of people to choose for themselves. Their society engineers these people so that they cannot choose anything, really. Their appearances, careers, entertainments and media are all filtered and chosend for them--there is very little in which they can assert their own free will over. Agency is not really in existence in any significant way in their society.
There are other possible themes for this novel too, and I provided a link below that will help a lot. Good luck!
There are a number of important themes in this work. I will look at a few of them.
First, Huxley focuses on how technology can be used to control people. People in the book are genetically engineered. Then, after birth, they are conditioned to behave in certain ways by shock treatments. They are also provided with soma to deaden their feelings.
Second, Huxley looks at controlling people through keeping them ignorant and discouraging them from thinking. There are no books in the society and there is very little in the way of artistic expression. This is meant to keep the people from thinking so they will not become discontented.
Third, Huxley looks at the meaning of sex. People are encouraged to be promiscuous but to attach no emotional meaning to sex. This helps prevent people from forming bonds with one another.
If you look at all of these together, it is clear that a major theme of the book is the idea of government trying to control its people through a variety of techniques.