This is a short and non-spoiler review
The story follows a loveable little girl who lives up in the alps of Switzerland with her grandpa. The anime doesn't really have a overall plot until close to the end of the series. So if you like a anime which you can skip around a bit or watch a bit slower then it's perfect for you :) I personally like anime that I can binge watch but every once in awhile I sit down with my mom and watch it for a few weeks. The story is also great for families and young kids.
The animation is a older but it doesn't take away from the anime at all. The style looks different from anime nowadays but the slower animation adds to the charm.
I personally watched the German version of the show, and let me tell you the theme song slaps every time. The only reason I didn't rate it a 10/10 is because I don't really remember what other music, if any, was in the show.
The characters were all very likable. Heidi was a believeable kid, but that also means that she could be a little annoying to people who don't like kids. My favorite character was by far the Grandpa.
Overall, this is a great anime to sit down and watch together with your family. It is a very wholesome show and it also teaches a few life lessons