The tricky part of making this list for me is that I haven't read most of these books for a long time, and I remember little more than that I loved the book...so bear with me through my feeble reviews... Elementary School: Matilda, Roald Dahl (1988).
I loved everything Roald Dahl wrote. I think I've probably read all his books, including the books he wrote for grown ups. I think I read Matilda 10 times as a kid. Matilda was neglected, even loathed, by her parents but she found happiness in books. We were kindred little spirits (except my parents didn't hate me, they thought I was ok).
Junior High: Helter Skelter, Vincent Bugliosi (1974) and The Thief of Always, Clive Barker (1992)
Neither of these books are good. They're both garbage. I went back and tried to read The Thief of Always when I was in college, and thought "I was obsessed with this?" Yes, I was a morbid, dark kid in Jr High (and some of high school). I searched for books as demented as possible. I loved these books, and for a brooding kid in a podunk town, these were amaaaaaazing. Thank goodness I developed some taste as I grew up.
High School: The Grapes of Wrath, John Steinbeck (1939)
This is when I finally started to "get" literature. The Grapes of Wrath is my all time favorite book. It holds a special piece in my heart because this is where I cut my teeth on reading critically and learned how to interact with a book. Chapter 2, the chapter about the tortoise crossing the highway, is the most perfect chapter in all of American literature. It is the whole book, the whole era, all the feelings, all the thoughts, all in one little tortoise.
College: One Hundred Years of Solitude, Gabriel Garcia Marquez (1967)
It has been almost 10 years now since I read this book, so I suppose it's excusable that the only things I remember are that (1) this book is really hard to read, and (2) it is so worth it. It is amazing and mindblowing, but don't ask me what happened, because I don't remember. I just remember that everyone had the same name. After revisiting favorite books from my past and finding out they were actually terrible, I'm now more hesitant to go back and revisit favorites...but Oprah loved this one and put it on her favorites list, so it must be good for reals.
Law School: The Series of Unfortunate Events Books, Lemony Snicket
Law school involves reading all day and reading all night (followed by a career of reading all day, and reading all night). During leisure reading time, I needed a break. During those 3 long years, I read a lot of young adult novels. They're fast, easy reading, and a lot of fun. The Series of Unfortunate Events books are intelligent. Lemony Snicket (aka Daniel Handler) is a master at cross-writing his works for audiences young and old. While the stories are enjoyable for little ones, they're also full of sharp literary and political wit for grown-ups. Yes, you may feel silly checking books out of the children's section of the library, but check these ones out, they're well worth it. YA may well be my favorite genre. Other YA series you should NOT miss: His Dark Materials by Philip Pullman, and The Hunger Games series by Suzanne Collins.
20s: The Time Traveler's Wife, Audrey Niffenegger (2003)
Over the last few years, I've been reading a lot of fiction bestsellers. It's easy enough to pick one up at the big fancy display at the library, or Costco, or the airport, or wherever I happen to be. I can't say that The Time Traveler's Wife is a work of timeless literature, but it is a really, really good read. I love having that feeling where I want to keep reading, where I want to put everything else aside and just read this book, because I'm really enjoying it, and I want the whole rest of the world to just disappear. I think I got through this book in like 24 hours, and yes, I cried a few times. Do yourself a favor and skip the movie, the movie is terrible. The book, though, is fantastic and it is well worth it to set aside a weekend to get lost in it.
Honorable Mentions: In Cold Blood, Truman Capote (1966) and No Country for Old Men, Cormac McCarthy (2005)
I still like crime books, but unlike my Jr. High self, I now actually have taste. Each of these books are amazing. They juxtapose smooth prose with unspeakable horrors. The effect is enchanting. These are the books where I get to the end, and I am so sad, because the book was so amazing and now it's over.