Generally speaking, the understanding among historians is that the main arguments of a book should be backed by sources and cited. For example, in his book, "Past Imperfect", Peter Charles Hoffer lays out how American history developed since roughly the turn of the century.

Hoffer's main argument is that history moved from being largely consensus based to New History. Consensus based history was self-referential. One historian would develop a thesis and put it into words, usually with some archival research to back them up. Other historians would accept this as true and reference it without looking at the sources themselves, and the cycle continued. In the 60's, however, a rising wave of student activism and increasing enrollment in colleges gave rise to a new historical conscious. This new conscious, or New History as Hoffer calls it, argued that historians should put their histories up for scrutiny and criticism from other historians. Thus, the sources one used would at least be judged by others in the field, rather than accepted as true and accurate.

This New History survives today, albeit with some major developments. Professional historians have developed an expectation that arguments will be backed by sources and evidence, and that the details of an argument are not falsified.

Now, in terms of narrativism (i.e. putting the facts and evidence into a narrative form) the verdict is still out. Some historians argue that history is supposed to get to the truth of the past in some way (Edward Carr and Eric Hobsbawm both subscribe to the idea that the truth in the past can be seen through the lens of Marxism) while others argue that history is only a literary production that won't ever get to the truth (Hayden White and R.G. Collingwood sit in this camp). So while specific evidence is indeed needed for claims, the presentation of that evidence in a narrative form does not have a singular understanding.

This is a great question and I hope I have added some insight!