Depends on what you mean by "grab". Not every story needs to start with an action sequence, a mysterious, philosophical line, or some other gotcha, but something about the book should, within the first few sentences, communicate why the reader should keep reading.

My book starts out slow. It's an adventure story, and the first part spends time establishing world building through a subplot that explores my main character's status quo. The subplot resolves itself by feeding into the main plot of the story. Still, my book is j first person present. The main draw and constant, in my opinion, is my main character, her personality, her voice, and her flaws. So my first line is actually built around selling that, and not, say, getting the reader immediately into the plot