How do the writers who write history books come to know about the history that they are able to write a book ?

Answer 1

There is what is called "primary research" in history. "Primary" sources are
(a) physical evidence, including archaeological digs, visible structures, genealogical data;
(b) written materials such as documents [e.g. charters, Cabinet minutes, correspondence];
(c) in modern times, information in other media such as broadcasts, audio tapes, films, photos;
(d) oral information such as legends, people's opinions.

Historians gather and interpret, and reinterpret, primary sources. Of course they also read "secondary sources", which is what other historians have written, and sometimes come to new conclusions entirely from these.

Answer 2

They read other authors' books, including those written by people who lived in the times they write about. They also interpret physical evidence recovered during archaeological digs.

Answer 3

Makes me wonder why so many history books "REVISED editions."

Answer 4

By doing reasearch and reading HISTORY BOOKS......