Amazon lists this book (which I read on my Kindle) as “Wool Omnibus Edition (Wool 1 – 5) (Silo Saga)”. Under Amazon this book received 5895 customer reviews from many happy readers.

To call this “science fiction” seems for me a stretch. Nor are either “fantasy” or “apocalyptic” entirely accurate. Judge for yourself in this summary:

In a post-apocalyptic Earth the story takes place in a silo. But this silo is an inverted silo that begins at ground level and descends for something like 150 stories. To travel in this silo you must WALK on the spiral metal staircase. Inside this silo world unto itself there are living spaces, farming spaces, mechanical maintenance spaces, and the list goes on. Technology has not advanced from the time of the apocalypse so you will be familiar with all the terms.

From the start you are witness to one of the regularly occurring death sentence executions known as a “cleaning”. Only from observation windows can the inhabitants see the outside world. “Cleaning” means you are sent out of the silo to clean those observation windows. You always die during the effort.

After settling into this very confined atmosphere you learn of a suspicious death. At about this time Juliette, the heroine of the story, emerges.

That is all I will tell of the plot which unfolds with incredible descriptive attention to detail. Think of the story as a mystery one of whose goals is to discover why and how this silo came to exist. After 550 pages you too can know the answer.