If you decide to only read one book that I mention in these series of posts, you should read Lies My Teacher Told Me. But if you decide to read two, I have no problem saying that A Distant Mirror should be that second book. And the only reason that I think Loewen wins out is that his subject matter is a little more relevant than Tuchmann's, though some might argue with that.
Despite what the cover says, Tuchmann focuses her story around one very successful French nobleman, and uses the unfolding story of his life and times to highlight broader trends. Especially in the early chapters, this means that she is frequently pulling back from him specifically in order to highlight some cultural, social, or technological aspect of the world that is relevant to the story at that point. There are also sections where he is offstage as she explains the political drama happening elsewhere. But the book is well focused enough that these never feels like a distraction, and the story stays fairly cohesive
Seriously, Tuchmann is probably the best historical writer I have ever read. Back when I could still leave my books at work on the weekends, and usually did, I more than once ended up bringing A Distant Mirror home because I didn't want to put it down. It was 600 pages, and I was sad to see it end.
One of the things that...it wasn't bad, but struck me kind of funny, was that Tuchmann will occasionally make a witty quip. This happened the most in the beginning, and I almost wondered whether I had mistakenly purchased a Terry Prachett book. Fortunately, unlike the one Pratchett book I've read, the quips weren't overkill. They aren't a selling point for me, usually, but they might be for others.
Tuchmann does a good job of trying to balance and explain all sides of a conflict. This is most delicate when she is talking about the church, which at the time was experiencing schism, simony, and some extremely cynical dealings at the top. Tuchmann points these out because they're relevant, but doesn't dwell on them, and does include descriptions of the good works that the church was accomplishing at the same time.
I really don't know that I have much else to say about this one. I can only keep repeating "SO GOOD! READ IT!" for so long before we all get tired of it. If you have any interest in European history, I'd say this is the gold standard, so go get a copy already!