Hyperion by Dan Simmons is considered one of the best modern sci-fi books written.
Here are the pros and cons if you are considering reading the book.

Why you may not like it // Why you will love it
Here is my non-definitive list with reasons which could either make you love the book or loath it.
Worldbuilding…The book features many undefined terms which makes it difficult to understand.
Names of new technologies such as fatline and farcaster are thrown around without definition. There are many names for societies and organisations such as TechnoCore, Hegemony, and Ousters, which are mentioned and not explained. Those well-accustomed to world-building will be used to this (understanding that these unfamiliar concepts and names will defined later on, and understanding that if the story were to stop and define every term as it is introduced would firstly slow the story down to a glacial pace but also not be true to the character’s perspective who may be familiar with the term used).
Poetic, flowery language.
This is not the straight-forward, functional writing style of Brandon Sanderson. The writing is beautiful and descriptive, spending time setting the scene and building the landscape around the characters.
Many short stories fit into one larger story.
As Hyperion was modelled after The Canterbury Tales, it tells the backstory of each person in a group of travellers, from their perspective. Each story is told as a self-contained narrative and is written in a different style. Some are written as journal entries, others as narratives. The detective’s perspective is short and sharp, while the philosopher’s perspective is drawn-out and focuses on the emotional impact.

A wide cast of characters who have different personalities, goals, and backstories.
You either like stories with lots of characters, or you prefer to stick in the mind of one person. There is no right or wrong, it is just your personal preference.
Intertextuality.
This is just a big word which means that this book is shaped by other books. Hyperion mentions a lot of other existing works of literature. So, to understand the depth in this book, you must understand the other books and texts it references. Just to name a few references, we have the poems and life of poet John Keats, the story structure is based off The Canterbury Tales, the tales of Abraham and Isaac in the Bible, and the names (such as the tree-ship Yggdrasil) are based of ancient mythology.

It is unlike what you’ve read before.
The author experiments with different writing styles, different techniques and different ideas. At times, it seems experimental and unusual. If you’re looking for a run-of-the-mill, cut-and-paste sci-fi where you can relax your brain as you read, then you probably won’t like Hyperion.
Detail, detail, detail.
There is A LOT of detail. Blink and you’ll miss something important. You must concentrate when you read it because something small mentioned may be HUGELY important later on.
VERDICT
Hyperion and The Fall of Hyperion are two of my favourite sci-fi books of all time. I recommend it, but I know it is not for everyone. While I don’t have as positive things to say about the other two books in the series (Endymion and Rise of Endymion), the first two books are worth the read.
Recommended for those who like:
· World-building and detail
· Complex, gritty, realistic characters
· Stories from multiple character perspectives
· Beautiful, expressive, varying prose
· A strange avant-garde story