The book is about a man who doesn't have any friends and a woman who has an incurable disiease.
The two main characters in this story are a man without any friends and a woman with a fatal disease.
ーThe book is about a man who doesn't have any friends and a woman who has an incurable disease.
「その本は友達のいない男と不治の病の女についてです」
The book is about ... の言い方で本を説明することができます。
incurable disease で「不治の病」
ーThe two main characters in this story are a man without any friends and a woman with a fatal disease.
「この物語の2人の主人公は友達のいない男と不治の病の女です」
main character で「主人公」
fatal disease で「不治の病」
物語の主人公に重点を置いて話すなら、このような言い方もできます。
ご参考まで!