The middle of the book is supposed to be enjoyable. (Or at least worthwhile reading, in some way or another.) There are a variety of reasons why these enjoyments can't be in the start. Foremost, the start lacks context. Another problem is that there can't be a setup. Or, put another way, there can be a setup, but it will be the start, and it will probably be boring.

I think one "enjoyable" thing in the middle of a book is being profound. Or at least saying something interesting. However, I would also say they have to be earned and a part of the story. So nothing at the start is going to work for me.

There is one exception. It can be called surprise, a twist, something unexpected, or a change in direction. It can be done poorly, but it can also be done well. And it's rare, but apparently it can fit into even a first sentence.

We always seemed to be moving, always for the better, always to make our lives better, whatever. (A Very Large Expanse of Sea, Mafi)

This starts out ponderous and ends up cynical.

There are gods in Alabama: Jack Daniel's, high school quarterback, trucks, big tits, and also Jesus. (gods in Alabama, Jackson)

That actually twists twice.

And at least two classic starting sentences, which are also long, end with a twist: Catcher in the Rye and A Tale of Two Cities.