They say the first line, first paragraph, first page, is the most important part of your book. They’re wrong.
You don’t write an engaging, fun, interesting “first” part, and then get lazy the rest of the way. The entire book should be the most interesting. You don’t want your reader to say “The first page was my favorite part”, you want it to be hard for them to decide. You want them to say they love the characters, the dialogue, the worldbuilding. If their favorite part is the beginning, you’re doing it wrong.
The idea that you need a perfect hook is a reasonable one. You want people to pick up your book and want to read it as soon as they open it. It is, ultimately, a sales tactic. And plenty of authors and publishers who know a lot more than me will tell you that your job is to sell your book. I disagree.
Your job is, first and foremost, to write your book. Tell your story. That’s it. You’ll never write a hook that makes your story impossible to put down. You do that for the entire book. More than that, though, you will never write a single sentence that is capable of catching the interest of everyone. Because stories are personal, and they’re meant to be personal.
The whole book should be engaging. I don’t mean constant tension, I mean constant fun. You have to build up and release the tension in waves, and you have to make it enjoyable to read, not stressful. I don’t quote the lines that broke my heart or scared me. I quote the ones that inspired me or made me laugh.
There’s a balance you have to strike, to make the readers care. And you cannot make every single person who reads your story care. People are individuals, and there is not a single topic that every person on this planet can agree on. So I think we’re focusing too much on how many people we can reach. Don’t water down your writing to please a wider audience.