I asked my advisor the same question when I was working on my thesis. What they told me is that it depends on a number of factors, one of the biggest being the exact subject you are trying to study. The work i was doing at the time was on the 14th century English military, and my advisor was also an English medieval historian. Here it is important to say that 14th century England is a subject that has received a high quality of scholarship for a long time. This is especially true of the 14th century English military. There are a number of important works published around the turn of the 20th century that remain important and oft citied works in the field. This isn’t to say that there isn’t ongoing debate in the field, or that older works aren’t being challenged, but older works remain relevant to the ongoing discussion and are not being widely discarded as out of date. New work tends to add perspective and nuance to older scholarship rather than overturning it entirely. In part this is a symptom of a relative abundance of accessible, published primary sources that have been available to historians for a long time.

By contrast, I took a class in grad school with a historian who’s primary field of study was the crusades and holy war. He was extremely leery about touching any secondary sources published after 1980. There were exceptions of course, and it was certainly not a hard and fast rule but it spoke to a general bias against earlier literature in his specific field of study. There is some exceptional work on the crusades from the early 20th century, but a lot of earlier publications are tainted with various issues. Some of this stems from relative lack of access to primary sources (especially from the Muslim perspective) that was available to earlier historians, but some of it also stems from the ethnocentric and Eurocentric trends that are common in history as a discipline. It’s not that older scholarship on non western subjects is bad, or that it’s not useful, just that it needs to be evaluated more carefully and in a specific context.

There is also a question of scope here. Writing my thesis I was writing a serious work of original scholarship that required me to have a deep seated understanding of the historiography of my topic. For the other professor I was writing research papers that, while substantial, did not require me to understand the topic as thoroughly. Historiography is important, and understanding the way that views on a topic or in a discipline have changed and evolved with the progression of the field is an important part of doing good history. In that regarded older works are always valuable and if you are going to undertake serious academic level history, you should absolutely read all the quality scholarship you can get your hands on regarding the subject. However, if you are reading for fun or to acquire a general overview of a subject you can usually save yourself some trouble by skipping to modern scholarship.

At the end of the day history is always evolving and new sources and information are emerging all the time. While older works can be excellent works of history, they ultimately can only work with what they had available at the time of their publication. Obviously more recent works build off of the work that preceded them and often include an analysis of important older works on the subject and reading more recent work will save you some trouble. There are, as always, exceptions to this and some older scholarship is truly next level and worth reading for its own sake but as a rule for the causal history enthusiast modern works are often less trouble than slogging through the whole of the historiography. You can always mine the footnotes and read older works citied there that catch your fancy.

As far as your specific book, google it, look up the author and his publication history and see what the consensus of his work is in general. Ancient history is tricky, and it is a field that has received substantial attention since the dawn of modern history as a discipline. Recently there has been a far amount of revision regarding some common arguments in the field.

I hope that answers your question!