It depends on various factors. If it has been widely promoted, translated, and has received critical acclaim, then it could be well - known. However, if it's a relatively new work or has not had much exposure in the mainstream media, it might not be as well - known. Also, the popularity could vary from region to region. In some areas where the story's subject matter is more relevant or interesting to the local audience, it might be more well - known.
I don't think it's a household name. There are many works based on true stories, and only a few achieve mass popularity. 'Ehrengard based on a true story' might be known among avid readers, especially those who explore less - known literary works. It could be that it has a small but dedicated following. Without more information about its distribution, marketing, and reception, it's hard to say for sure whether it's well - known or not.
I'm not sure if it's widely known. There are so many works out there, and some that are based on true stories can be quite niche. It might be well - known in certain circles, perhaps among those interested in historical fiction or the particular genre it belongs to.