You will agree with me that when you read a book, an essay or research paper on a certain topic, somehow you always imagine that the writer is a professional in that field (that he is writing about). It may be true in some cases, but in most cases that is not always the case. A writer may be prolific in writing about a certain thing-this is mostly common among UK writers who are employed in the media houses-but in reality they may not uphold the same or worse still may not know so much about the topic in question other than the face value of it.
A good example is when an author writes about experiences of war in the first person as though he was actually on the ground as an army officer or soldier when the war was on. People reading the story may be captivated by the story (which is alright as it is the primary target of the writers), but they may also associate the writers with the story and imagine that it is indeed true that the writers know so much about war. From my research this is not true at all because as much as the writers present themselves as the know-alls, the reality is a different scenario altogether. Jeffrey Archer has written many Crime thrillers, but it remains to be seen if he can marshal a troop of soldiers into war.