Just an fyi, adults may enjoy the FB series more because it deals with more adult things from the get go. I will say this, 90 percent of adults that have never seen a single movie or read the books that I have talked to personally and gave it chance seemed to enjoy them even if they were not into magic. If you think you are to old for the series, the truth is every age become a fan of HP. I would say that if you know nothing on the series but may want to give it a chance, I would recommend two things. First watch movies 1-3. The first two are childish but the third is when it becomes dark and number becomes really adult like. 5-8 is not meant for kids. It’s not all fantasy and some things take place in our world (watch the first one to understand the term muggle). The books have much more in them than the movies but the movies do the books justice. Secondly, if you go to the website:
https://my.wizardingworld.com/login
You can be sorted, learn your wand type (which can help before you go to the WWHP in FL or CA), and learn your patronus (but do the patronus test after you watch movie 3). It won’t spoil much if you do the three tests before you watch the first movie but it might confuse you until you do.
If you are on the fence about watching them in the future, here is the trailer for movie one: