I have found in my local library an incredibly useful world building source called the Culture Shock series (Survival Guides to Customs & Etiquette) and the Culture Wise series (The Essential Guide to Culture, Customs and Business Etiquette). You might be able to find them, or similar books, in the Travel section of your library. Why might they be useful, you ask?
Well, for those writing contemporary fiction, they’re useful because they can help you understand the backgrounds of certain characters in your fiction, particularly if your novel involves a lot of migrants, or is even set in another country. Historical writers will likely benefit from these books simply because they give you a basic idea of where the culture is now – and that might help you during your research of what they were like back then. Of course, proceed with caution as many customs may have changed due to influences of modern technology, international relations, and any number of other reasons.
For those who have to build an entire world, for their novel (science fiction and fantasy), these are a fabulous source of inspiration and ideas about other cultural perspectives. Instead of simply relying on the Modern White Western Medieval Perspective (a version of the medieval culture that has entered into modern popular culture and is likely quite inaccurate) for your fantasy novel, you can steep yourself in multiple cultures. You can examine the reasons behind their perspective, their customs and taboos, and see how they tie into the country in question. Then when you’re building your own world, you can edit and adapt existing customs that would already have a similar source. Your country is extremely hot, so perhaps even the slaves are allowed siestas in the shade, and there might even be water-bearers who ensure that there is water close at hand.
At the moment, I'm reading one on Tokyo, Beijing, Philippines, India, and Malaysia. I also have a dos & donts in the Philippines book. Ahh, a writer's reading list is never done...