This is the 308th most frequent Japanese word.
始まっ
The word "始まっ" (from 始まる) means "began" or "started" in English.
In this sentence, 始まりました (hajimarimashita) means 'has started' or 'began,' indicating the action of commencing an event, specifically the movie.
映画が始まりました。
The movie has started.
In this case, 始まっています (hajimattemasu) is used metaphorically to describe how the book starts, giving a descriptive context.
その本は冒険の予感から始まっています。
The book begins with a sense of adventure.
Here, 始まっています (hajimattemasu) means 'is in the process of starting or ongoing,' describing a continuous state of the beginning of the semester.