They tell us where the fishermen fish, how they fish, what they fish, and how they keep the fish alive. They also tell us how the fishing industry in Hong Kong grew, became the best in the region, and then lost to the industrial scale fishing from China. They tell us how the fish around Hong Kong are fished to extinction.
And they tell us much more. Such as the meaning of: 汆水, 開新, 威也, 翕你過嚟, 樁下樁下, 賴住佢, … I actually knew most of these expressions when I was small and hanged out in Ap Lei Chau often.
They tell you about: 牙帶, 馬友, 木棉(大眼雞), 石九公, 白飯魚, 泥鯭, 紅衫, 青衣, 蘇眉, … They tell you what they look like, where they are from and what they taste like.
If that is still not enough to get you to go out to buy the books - these are some of the best books I have read about local culture written by local people. For this reason alone we should buy the books to support the local culture.