I recognise this is a very broad question and likely one with no real answer, but I thought I'd at least try asking. I've recently becoming interested in reading about a variety of historical figures, but there doesn't seem to be an obvious way of verifying the credibility of biographies or even just historical writing in general, at least for laymen. Of course, certain books will get published reviews, though rarely, and I could check the reviews on Amazon or Goodreads but I have no way of knowing if the reviewers have the credentials to really comment on the accuracy. Obviously, this very sub might have recommendations, but I don't want to spam it every single time I want to read about a new historical figure. Perhaps there's no solution - thoughts?
A biography is a history. Yes, it's of a particular person, and because it ought to place that person in their world, it ends up having to be more than a history of them. So, the same sorts of rules apply to biography : good ones get some peer review, get noticed. You can do a basic research on this pretty fast: do a Google search under the author and title, along with "review" , and see what comes up. There may be a lot of blog entries, but even those sometimes are by scholars. And a good review, in some place like the New York Review of Books or the London Review of Books, will itself often be a good introduction to the subject.
There are other tricks as well. Is the publisher someone scholarly, like Oxford University Press, or is it unknown? Are the blurbs on the back by other scholars from respected journals?
Or use Google Scholar, and then you'll find out something about how often the biography is cited in other people's work. This can be handy for separating scholarly from popular, good from bad. For example, type in "Ulysses S Grant" and "McFeely", and you will see 429 scholars- many of them historians- have cited McFeeley's bio Grant. If you type in "John Lennon" and "Albert Goldman", you'll find that 134 papers have cited Goldman's The Lives of John Lennon- which seems OK until you look and see that few of them are by historians. And, looking though the article listings below that, you'll see that his biography was more than a little controversial, with one New York Times article titled "An Embattled Albert Goldman Defends His Book on Lennon". So, clearly McFeely's book on Grant is pretty accepted, Goldman's book on Lennon got slammed. But, note that this doesn't mean you shouldn't read Goldman: it might be very interesting- but you likely would not want to rely on it for a careful story of Lennon's life.