In your explanation here, you say that you have to relate Marx's theories to the book. I would say that you should do this by saying that this society shows what Marx says is wrong with capitalist society. This society is not marxist. Instead, it is the epitome of what Marx is criticizing.
To Marx, capitalist society has the upper classes dominating the lower. In this society, this has been taken to an extreme. The upper classes (the Alphas) create these castes of slaves to do their work. To Marx, religion is used to prevent the masses from rebelling. In this book, conditioning, sports, soma, and sex are used for the same purpose. When you look at it like this, you can see that Marx would say that this society is like capitalism, only worse.
A truly marxist society would have a population that is all equal. This does not exist at all in this book. So I would argue that you should relate Marx's theories to this book by saying that the book portrays a society that is a caricature of what Marx criticizes about capitalism. It is meant to show what society ends up like if we take capitalism to its logical end.