I just want to understand what "kind" of books are most reliable and worthy to be quoted, whenever you are looking to settle a historic debate?
What is exactly an "academic source"?
A book from any professor of history from any university, or an esteemed university?
A book from an esteemed professor, former professor, or even someone who has no experience in teaching?
How do we establish the credibility of any given book written by any given professor, can it not be subjective sometimes?
Or does an "academic source" strictly mean books like these:
https://www.cambridge.org/gb/academic/subjects/history/military-history/european-warfare-13501750?format=PB
Cambridge university has got various of such books. These "Cambridge History" books that come in almost all of various subjects of history, are currently my "goto books" for whenever I am looking for any sort of question that I can't find a definitive answer about. Am I correct to do that?
Follow up question.
Those Cambridge History books don't in particular say they have an "author". But mention various "Editors".
How does that work?
So, there's no hard and fast way to tell if something is reputable academic history (and you probably shouldn't trust anything you read unconditionally), but here are some things to look for when making judgements about reliability:
Is the publisher reputable? Many academic history books are published by university presses, generally speaking the more famous the university the more exclusive the associated publisher. So if it's been published by Cambridge or Harvard University Press, that's an indication of quality, but generally speaking anything published by a university is likely to meet reasonably high standards. Many other big academic publishers are international brands that can be easily googled. All of these should have quite stringent editorial and review processes in place.
On the flip side, if it's a small press or one that seems to publish a lot of stuff which doesn't seem particularly scholarly, that's a sign to be cautious. Same goes for something that is self-published. In these cases, there's no guarantee that the work has been reviewed by someone who knows what they're doing. That doesn't mean you can dismiss it out of hand, but rather to be extra careful.
To answer your follow up about the Cambridge series, such books are designed as introductions to broad topics. They'll usually be edited by established experts in the field, but individual chapters on specific topics will be written by individual authors. Generally speaking they are very high quality, but more introductory than most academic publishing, introducing you to a range of perspectives, debates and issues in a field, and featuring less primary analysis.
Who wrote the book? What qualifications do they have? Are they affiliated to a university or other institution? Again, these are not guarantees of quality, but if the author has a PhD and works at a well-known university, it's less likely that there are going to be serious flaws in method or evidence. The absence of these qualifications doesn't mean that a book is worthless, but it is again a sign to treat it more critically.
This is probably most important when judging a work of history: is it giving you enough information to evaluate the claims being made? Does it use (sufficient) footnotes to show where evidence is coming from? Are all claims supported by traceable evidence? Does it have a bibliography of primary and secondary material the author has consulted? The point is not to trust a footnote uncritically, but rather that you know you can, if needed, resolve any doubts by following things back to the source and checking for yourself. Conversely, the absence of footnotes/endnotes or a bibliography is a sure sign that the work should treated extremely sceptically. Not only are you having to put your full faith in the author, it means that any review process the work has gone through couldn't be effectively evaluated by even an expert reader. In the words of my undergraduate history society t-shirt: "until I see a footnote, that's just an opinion".