For me, these come instantly to mind:
First, Lord of The Rings. I was 10 when I discovered it, and I devoured it in great gulps. I probably didn't understand half of it -- I know I skipped a lot; I wasn't a fan of long battle sequences -- but what got me was the world. It was real. That was all there was to it. I was positive that Middle Earth had once really existed, and that if I could just go back in time somehow, I could live those adventures along with Frodo and Strider. I even had the exact rendezvous point decided: I'd meet up with them at The Prancing Pony in Bree. (I think I even worked out the date, though of course it was in the Middle Earth calendar. Minor technicality.)
Yes, it's true: I was the sort of child who, even at 10, half-believed in going back in time. I was also the sort of child who would skulk through the woods near her house with a 'knife' made of stone, pretending to be one of the Lord of the Rings characters. I'd have died of embarrassment if anyone had seen me; I was laughed at enough at school already. But it still felt very real. Tolkien's work had touched something deep inside of me that had needed nourishing, and gave me a love of fantasy that has never ended.
From there I found the work of Tove Jansson (moomins!). And Carol Kendall's The Gammage Cup. And C.S. Lewis and Narnia, of course.
As a quick aside, I don't know how the Narnia series is published in the US now, but the editions I had back in the 70's didn't Americanise the text. There were still words like 'bluebottle' for 'fly', and 'row' for 'argument'. My father scribbled notes in the margins to translate all of this for me, and I LOVED it. The exotic-to-me words were part of the appeal: the sense that these stories happened someplace that was not the US, and gasp, shock -- they said things differently there! Pure magic. I'm painting with a broad brush when I say this, but in general I think it's deeply misguided to homogenise stories. Hey, let kids know that their immediate world isn't the only one that exists. This can only be a good thing.
Lloyd Alexander's The Prydain Chronicles was another series I wanted to step into and live in forever. If you haven't heard of Lloyd Alexander, you're probably reading this in the UK where he's not well-known, even though he totally should be (and his Prydain stories were inspired by Welsh myth). While it was the world itself that I really loved in LOTR (oh, and Pippin and Merry: the only two who seemed to have a sense of humour), in Alexander's work it was more the characters. Taran the assistant pigkeeper. Eilonwy the princess (who was totally kick-ass and not frilly in the slightest; oh, how I wanted to be Eilonwy!). Fflewddur Fflam the bard. I had a huge crush on Fflewddur. Taran the hero was too bland. Fflewddur was funny and brave AND HAD A GIANT CAT FOR A STEED. Seriously, who needed Taran?
That was always my tendency, actually: to have a crush on the main character's sidekick, rather than the MC himself. Sidekicks were usually quirkier, with a better sense of humour; they seemed to have more intriguing pasts. I had a feeling that they'd be far more interesting to hang out with, even if they weren't as pretty.
Fantasy wasn't my only love; real-life stories had their place, too. One of my favourites was one you probably haven't heard of (but I'll be so excited if you have): The Secret Summer of L.E.B by Barbara Brooks Wallace. A blurb about it online says, "Lizabeth risks her popularity with the other sixth graders by becoming friends with the class outcast." And yes, it is about that, but there's so much more to it. The story is actually a very gentle romance; possibly one of the first I ever read. The class outcast is the truly lovely Loren, who got off on the wrong foot with the other kids and never recovered from it. I could identify with that; I was bullied myself in school until I was able to change year groups. AND Loren shared my love of Tolkien! He and Lizabeth bonded over hobbits! They met in an abandoned house which they began to fix up together -- and that idea of an abandoned place that you can call your own reappears again and again in my own writing now. In terms of the romance, all that happened was that Lizabeth and Loren eventually held hands, but I copied that passage out in my diary and swooned over it. I wanted a Loren for myself.
K.M. Peyton was the first author who broke my heart. I was addicted to her Flambards series, and SO in love with Will. (Spoiler alert!) When he died at the start of the third book, I literally couldn't believe it. I remember feeling cold, and immediately shutting the book and putting it back on my shelf. I couldn't bear to read it, not without Will. It was literally years before I picked it up again....and then, of course, I fell in love with Dick. And then discovered later on that there was a FOURTH book, where Christina's marriage to Dick doesn't work out and she falls in love with MARK. It was enough to make you dizzy, but Peyton pulled it off with her absolutely honest writing. I always imagined that she got Christina and Dick together at the end of book 3, and then started thinking about it: would that really work out? What would actually happen? (I met Peyton at a publishing party a few years ago, and was utterly tongue-tied.)
The Outsiders by S.E. Hinton spoke to me with its grittiness and sense of truth. I sobbed over Johnny's death, and remember writing in my diary that I longed to be a writer of similar power someday: someone who could make people cry. I didn't know, then, that tears are sometimes easier to achieve than laughter. I hope I manage to do both now.
Finally, my beloved Barbara Wersba. She's another one you might not have heard of if you're in the UK, but her Tunes for a Small Harmonica saved my sanity as a teenager. Like authors Judy Blume and Norma Klein, Wersba said to me, You are not alone. The things you feel are perfectly normal.
And she was FUNNY. And bittersweet. And quirky. I love all her books, but Tunes was the first I discovered. If you've never read her work before, check it out. Believe me, you've got a treat in store.
Looking back at all of these, it's probably no coincidence that I now write fantasy which is heavily rooted in real life: the world as we know it, but with a twist. (And with romance, of course!) The books I loved growing up created that landscape, and I owe them so much.
What books have shaped you? Tell me -- I'd love to hear about them.