For me it was The Story of Ferdinand, by Munro Leaf. My memory doesn’t go back as far as when I learned to read, but my sister caught me looking at it one day. She thought I was actually reading the book aloud until I forgot to turn a page but kept on “reading”… 
Other books I remember reading at around the age of seven or eight were the Nordhoff & Hall Bounty trilogy, The Guns of August, and Zane Grey’s The Last Trail. Any of those could have been the first “adult” book I read.
The very first? ‘Harold and the Purple Crayon’ - I was 6, probably. I caught on to reading from the very beginning, and there was no stopping me. I went to the library every week and got stacks of books, and later read a lot of things I maybe shouldn’t have, at a young age (my aunt was a librarian and I had free run of the place.)
Stunning pictures in Misty of Chincoteague, later I dabbled in The Black Stallion series. And National Velvet, which was written in England in the 30’s, and tough sledding pre-internet (I had to guess at some of the slang, etc.) - but I still loved it and the movie version.
The first I remember was Yertle the Turtle by Doctor Seuss.
I also read a lot of the Landmark books and their science book parallel, All About books. My grandmother got me a subscription, so I got them every month.
My elementary school had a section of biographies. I believe this was a series (this was early 70s). I seem to remember I focused on the sports people. But, the only one I specifically remember was one on Booker T. Washington.
I remember the first book I took out of my elementary school library when I was in Kindergarten. It was Indian Two Feet and His Horse (which I’m sure is inappropriate these days).
As for novels or chapter books I read all of the Beverly Cleary books, Marguerite Henry books (numerous times), The Velvet Room (numerous times). I bought/red every horse book offered by the Scholastica book club. I think there was a Weekly Reader book club handout I’d get at school too. I was so excited when we’d get the new book club handouts at school. I have to thank my mom for letting me get whatever books I wanted.
I don’t remember a specific book, but I remember our weekly walk down the block to the Book Mobile, a library on wheels.
Earliest book I can remember was The Magic Faraway Tree by Enid Blyton, before that it is all in fuzzy picture book crossover land.
Yeah, and I had a Ferdinand whose head turned when you twisted his tail.
I still have a soft spot for those books. I remember my mom reading them to my sister and me at a young age.
The first book in the series is The Enchanted Wood.
I really can’t remember back that far. I’m told that I was four when I learned to read. We had a lot of Dr. Seuss and picture books around, so very likely one of those.
When I started reading bigger books, I was really into Nancy Drew, and would also read anything that looked like it might be scary. There was a book at the Fort Lauderdale public library that I checked out every time I “found” it again (I could never remember the name, and probably didn’t grasp the concept of locating books on purpose). That book was
Ghosts and More Ghosts, by Robert Arthur. I’m proud to say I have my very own copy now!
The first “real” book I remember reading is The Illiad.
In ancient Greek?
Spanish!
The first book I read for myself, fluently, was Charlie and the Great Glass Elevator. Since WW and the CF first appeared on tv on November 28, 1974, I suspect I read Charlie and the GGE sometime in December 1974 (someone had taken the Chocolate Factory out of the library before I got to it - but the Elevator was right there).
Me, too! It was third grade, and my teacher, Mrs. Vogler, had an hour reserved twice a week when we could each pick any book we want and lounge on the carpet she had in the middle of the room and just quietly read (she was a great teacher).
On the shelf of books to choose, I saw Red Planet: A Colonial Boy on Mars. To me the word “Colonial” meant only one thing–the Pilgrims and the American Colonies. I pictured a Pilgrim boy transported from Plymouth Rock to Mars and somehow that really intrigued me.
Of course the book was quite different than that, and of course it was SO much better than that silly idea. I noticed the sticker on the spine of the book (It was yellow, and had a stylized atom and a rocket ship). That sticker was what I sought out at the public library from then after–and it led me to the rest of the Heinlein juveniles, to Asimov, Bradbury, Norton, and so many others. A lifelong and rewarding love for SF started with that book.
Anybody remember reading The Five Chinese Brothers? I thought it was hilarious when I was in kindergarden and first grade.
I think I had that book too. Was it published by Classics Illustrated? Mine had the story of the hitchhiker who borrowed the driver’s sweater, later found draped over her tombstone.
This is another book that scared the crap out of me. I couldn’t get to sleep if it was in the same room…
Kid’s book - The Skull That Talked
Adult Book - Jaws
Nope, Ghosts and More Ghosts was all original tales by Robert Arthur (who also wrote the Three Investigators series). He edited some horror anthologies, though, so maybe it was one of those?
The story in my book that scared me the most was a story about a radio host who did a live broadcast from a haunted house. He did such a good job harnessing the power of his listener’s imaginations that… oh, something very bad. 