What's the Name of That Book??? discussion

I read this book in 2018-2019, and so I'd say it was published in 2005 or later. The story is about people who live in a tower. This tower is very tall (I could be wrong, but I'm 80% sure it is exactly a mile high), and what level someone lives on determines their "social status"; The higher the floor they live on, the higher their status. The tower isn't just an apartment building, but it also has a lot of everyday things like restaurants, parks, actual houses on each floor, gathering places, etc. The pov is third-person omniscient, as each chapter switches characters. The daughter of the tower's owners (the owners and their daughter live on the top-most floor) is a "designer baby" - she is supposed to be perfect. She has friends who are near the top of the tower (creating an "elite social group"). The story also has characters who live at the bottom of the tower, and are "poor", and the story shows their struggles.

The cover has a tower on it and that’s it. It is a modern looking tower. I think it is black/gray but not certain. It is a 2-3 book series (most probably three).

I can't remember the plot, but it revolves COMPLETELY around the making and breaking of relationships and power struggles.

One relationship I remember existing (because at the time I didn’t know what incest was) is the “designer baby” and her brother being in love with each other. This was in the first book. In the second/third books, the brother goes away somewhere and they don’t love each other anymore.

One phrase I remember is something along the lines of “the higher you go the harder/faster you fall” I’m not sure if this was a quote in the book, but I think it was on the cover/on the back as a “catch statement”

This book would be YA fiction.

SPOILER

At the end of one of the books, one of the "elite" characters is at a party of the "designer baby" girl on the top floor, and then she goes above the top floor outside the tower and jumps. I think it is the first book because this scene ends in a cliffhanger and the next book continues from here.

The subsequent books include a trip to a foreign country where the daughter (“designer baby”) goes too. Don’t really remember anything about this though.

I’ll keep adding more stuff as I try to remember more.

Anything helps! Thank you

EDIT: It's not "The World Inside" by Robert Silverberg, although it is very similar

Sounds like possibly The Thousandth Floor by Katharine McGee; apparently it's the first book of a trilogy.

Denis wrote: "Sounds like possibly The Thousandth Floor by Katharine McGee; apparently it's the first book of a trilogy."

YES!! Thank you so much!

Glad to help. Folks on here helped me find a book I'd been looking for off & on for over fifty years.