My suggestions for teens:
Harry Potter by J. K. Rowling - I was in high school when the craze was at its height, and so I consider myself a part of the Wizarding World Generation. Honestly, though, you cannot go wrong with Harry. This is a cliche suggestion, by now, but it's still the best book series around for a reason. I, for one, credit Harry as one of the reasons I am a reader today. If you haven't given these books a try, then you're missing out.
The Perks of Being a Wallflower by Stephen Chbosky - I read this in high school (as did many of my friends), and it helped me feel strong through some of the harder times during that period of my life. It's great for high school freshmen who feel out of place, but fair warning that it contains references to drugs and sex. The movie version is also really well done.
The Hobbit and The Lord of the Rings by J. R. R. Tolkien - These are your classic fantasy books, and I love them all very dearly. I suggest starting with The Hobbit, which is my personal favorite in the series.
Illusions by Richard Bach - I feel that this is a book that kids in high school will appreciate. It's sort of a mind-bending book that helped me grow as a person. It's one of my absolute favorites.
The Unwanteds by Lisa McMann - This is just a really fun series that feels like the combination of Harry Potter and The Hunger Games.
Any of Edgar Allen Poe's short stories. Seriously, any of them. Go to your school's library and give Poe a chance. You won't regret it.
I, Robot by Isaac Asimov - The movie version of this book is... well not something I would ever recommend. The movie does not follow the book whatsoever. However, the book feeds a mind that craves intellectual wandering. It's a collection of short stories about the Laws of Robotics. It will make you think in new ways about the world.
The Hitchhiker's Guide to the Galaxy by Douglas Adams - A fun book series that will send you traveling on an adventure through space. These books are hilarious and fun.
Ender's Game by Orson Scott Card - A brainy story about a kid that trains to become a master in the art of space-war.
The Giver by Lois Lowry - This book is set in a dystopian society, meaning a should-have-been paradise that has a terrible underlying problem. I read this in one night during my years in high school.
Alas, Babylon by Pat Frank - A story of survival after an apocalypse of sorts. If you liked Hatchet by Gary Paulsen when you were in grade school, this is a book that gave me a similar feeling, but is aimed at older readers. Give it a try!
The Absolutely True Diary of a Part-Time Indian by Sherman Alexie - I actually discovered this book while studying education in college. Since then, I've come to love Sherman Alexie. If you like this book, check out his poetry and other work! He's great!For really young readers (kids below the age of 12), I firmly suggest any of these: Around the World in 80 Days, Journey to the Center of the Earth, 20,000 Leagues Under the Sea, Hatchet, or Alice in Wonderland. If I had young kids, these are the books I would read to them at night.
My suggestions for adults:
It by Stephen King - If you've never tried Stephen King, then yesterday was the time to start. This man is a master of crafting stories. The truth is that there are a million books out there, but even the lesser-loved Stephen King usually end up being better than 95% of what else is out there. My favorite book by him is It, and it's good for anyone who has ever felt stuck in a town.
The Good Earth by Pearl S. Buck - This is one given to me by a teacher in high school, but I would rather list this for adults because of its allusions to sex. This is a fantastic book about people in a Chinese village. It is one of the books I credit for turning me into a reader.
A Song of Ice and Fire Series by George R. R. Martin - This is like the Lord of the Rings for mature audiences. Never before have I read something that has struck my nerves as hard as the ones in this series. The HBO show is also fantastically performed. This is not a series to be missed out on.
I am Danger, I am Prisoner by Sergeant Danger Geist - This is a memoir written and self-published by a friend of mine, and it's a very honest look at the war in Afghanistan. It's great! You can read the first nine chapters on his website for free!
House of Leaves by Mark Z. Danielewski - This book was hard to get through but worth it. This book is about a guy who finds a trunk filled with the scattered pages of a book that is about a documentary that doesn't exist. If that sentence confuses you, then you should read the book. This is a scary book, and it will sit within your mind long after you've finished it.
Predilection by Mary Parker - My friend put together a collection of short stories, and they're really great. She's a master at horror, and this book is only a debut for all the things I'll bet she'll write in the future. You can buy a copy by clicking here!
The Weird Tales of H. P. Lovecraft - You can't go wrong with a short story by Lovecraft. If you love weird monsters and provocative settings, this will be a treat.
Things Fall Apart by Chinua Achebe - This is a book that will sink you into a culture that you won't be comfortable with, and it will give you a perspective about your own culture. It's about colonialism in Africa. This is a must-read, in my eyes.
Inferno by Dante Alighieri - This is a classic. Dante's Inferno is the first part of a longer work, but Inferno is definitely the most fun part. Evil is fun to read, what can I say?
So, those are my suggestions, but I expect this list to grow/change over time! You can probably tell that I love fantasy, science fiction, and horror! Hah! If you happen to be a writer that has stumbled upon this page and you wish to be included on this list, you should send me a message at my facebook page. Maybe I'll read your book (if it isn't romance, ha ha)! However, I'll only list books here are readily available for anyone to purchase (but I won't hate on you, even if I didn't like it). I might also do a review on Amazon for you if I do!