The best book that I have ever read in my entire life is Rules, by Cynthia Lord.

Rules spontaneously take you through the life of Catherine. More than anything in the world, all Catherine wants is to be a normal teenage girl, with a normal 8 year-old brother named David. David has autism, which drives Catherine crazy! Catherine is sick and tired of constantly being embarrassed by David throwing tantrums in public. One thing that you should know about David is that he LOVES rules! For instance, no toys in the fish tank, when someone says hi you say hi back, if you can only choose one pick carefully, at someone else’s house you have to follow their rules, and many others! Every Thursday, David goes to Occupational Therapy at the clinic. While there, Catherine meets Jason, a teenage boy in a wheelchair who cannot speak. Jason uses a photo album filled with many word-cards, so that he can talk with other people.

Over the summer, a girl Catherine’s age moves in RIGHT next door, like Catherine had always hoped! Catherine tries as hard as she can to be friends with the new girl, Kristi. Catherine eventually finds out that Kristi is friends with the bully on the block, Ryan Dushane.
Meanwhile, at the clinic, Catherine and Jason are becoming closer friends. Eventually, Catherine becomes torn between being a normal teenage girl with her friends, or staying behind to help David and Jason. This situation forces Catherine to figure out the true meaning of normal.
Specifically, the reason why I think this book is so incredible is because of how Cynthia Lord included so many thoughts and feelings from Catherine. For instance, it really shows how Catherine feels about having and autistic brother. It is highly unlikely that you will find a book about someone having a disability that is as amazing as Rules.
In conclusion, I think that Rules by Cynthia Lord is an amazing book for many reasons. So, if you are looking for a really good book to read, I HIGHLY recommend Rules for any age!