When Elizabeth Pisani set out to research her new book, “Indonesia, Etc.: Exploring the Improbable Nation,” she passed up any ambition to pin the vast archipelago nation down in a pithy manner. “We don’t even know how many islands there are,” Ms. Pisani said. Some officials say 17,000; others, 15,000. “It’s an extraordinarily difficult thing for even its own government to get its head around, let alone an outsider like me.”

Which is why Ms. Pisani made just one rule for herself during her many travels there: Say yes to any invitation, whether it was to a wedding or “to have tea with that dog liver and glass of rice wine,” she said. “That took me into very interesting directions.”

The resulting book is part travelogue, part history, and as fascinating as the country it describes. Below are edited excerpts from a conversation with Ms. Pisani on Indonesia.

Image Elizabeth Pisani. Credit... Marit Miners

Q. Where do you begin in a country as vast as Indonesia?

A. Java is a natural place to start. It makes up only 7 percent of the landmass, but is home to nearly 60 percent of population because the land is so fertile. The largest Buddhist temple complex on the island is Borobudur. Less well known, but every bit deserving of attention is another stunning complex of Hindu temples called Prambanan.