I think most kids somewhere between 6 and 9 years old depending upon the child might be ready for the first Harry Potter movie

My older daughter read these books originally because my wife bought her a set when she was learning to read well. These books helped her excel in her schooling. Now they might help my grandchildren too. They are very stimulating movies and books.

However, there are many many more details in the books and they are even more engrossing than the movies if you start reading them from the first book. However, the first 3 are best for children likely from 6 to 12 years old whereas the next ones after that are more life threatening and scary to watch and fall more into the realm of (Young Adult) which would be maybe 12 to 17 year olds.

However, it would be hard to find any series for children and adults better written than the Harry Potter books that I have ever seen.

When I was young I was drawn to Science Fiction that was Science based which would have been then Robert Heilein and Isaac Asimov and Arthur C. Clark and others like them. Then Gene Roddenbury and George Lucas also went into the Science Based Science Fiction theme also.

Books like I, Robot and STarship Troopers and others by Heinlein for example are what I read summers sitting out on the lawn or under a tree somewhere when I wasn't doing electrical work wiring homes and businesses with my father in his business. This then led to me becoming a Computer programmer and at one point later in life I was studying to be a Network engineer in San Jose near the Airport then before I got my heart virus and had to retire. So, technology has always interested me.

As a child I read popular Mechanics and Popular Science magazines so that I would have something technical to talk to my father about, especially from ages 6 to 12 years old. This led to science fiction by age 10 or 12 years old being my favorite genre. Later I watched loyally Star Trek on TV which was one of the best programs in the 1960s to be made for TV. And later in the 1970s in 1977 I went to Sunland, California to watch the first Star Wars movie with my then 3 year old son in my 1968 Camaro then in 1977.