Anyone who says a book is not hard to write is not really being honest.
"Forcing yourself to sit down, brainstorm, write, edit, rewrite, edit, cut, add, rewrite, workshop, rewrite, and rewrite some more until you've got somewhere between 50,000 and 100,000 words is grueling work" - and can't be called easy.
"A book takes time and effort. Many people feel overwhelmed in their work. The idea of writing a book seems like putting a great big rock on their shoulders. A great, big, heavy rock.
Writing a book takes commitment. Not merely time and effort. It takes focus. It takes getting out of bed and to your desk, every day, for a set amount of time, writing a set amount of words."
For more on this please visit:
https://www.nurturingbigideas.com/2020/08/why-is-it-so-hard-to-write-a-book.html
But if you have something to say and a story only you can tell - if you dream about penning down your story every minute of every day then go ahead - put in the hard work and finish the book.
Writing a book is it's in reward in so many ways.