I can’t choose! I was always reading when I was a kid.
All of the Marguerite Henry books
All of the Beverly Cleary books
The Velvet Room by Zilpha Keatley Snyder
TIL this about Caps for Sale:
“A direct sequel bringing back the monkeys, More Caps for Sale, was published in 2015, credited jointly to Slobodkina and her long-time personal assistant Ann Marie Mulhearn Sayer. This was followed by Caps for Sale and the Mindful Monkeys in 2017. The illustrations for the latter two books were created by scanning and editing images from Slobodkina’s original artwork.”
1. Swallows and Amazons, by Arthur Ransome
2. Tunnel in the Sky, by Robert A Heinlein
3. Star Rangers (akaThe Last Planet), by Andre Norton
Millions of Cats - Wanda Gag
The Good Master - Kate Seredy
The Black Stallion - Walter Farley. (tied with National Velvet - Enid Bagnold)
Illustrated Golden Bough
The Water-babies: A Fairy Tale for a Land-baby
Got my prepubescent hormones stirring 
Tom Swift
Quick top of head - thinking as a parent, not the ones I loved most as a kid
The Tenth Good Thing about Barney. Best book to broach death concepts ever.
One Fish Two Fish ….
Wrinkle in Time
As a kid, these three:
- Gift Bear for the King
- The Face of Abraham Candle
- The Search for Delicious
As a parent:
- Little Beaver and the Echo
- If You Give a Mouse a Cookie
- The Very Hungry Caterpillar
Very hazy memory of something about fog.
Little House on the Prairie
Holes — Louis Sachar
Alice in Wonderland
(My favorite as a kid was Tom Sawyer, but I haven’t revisited it in half a century, so can’t choose it with a clear conscience.)
The Choose Your Own Adventure series
Harriet the Spy by Louis Fitzguh
The Great Brain series
Mrs Frisby and The Rats of NIMH
I really enjoyed reading the “men’s action” book series published by Harlequin as a pre-teen but they are not “children’s” book.
The series included The Executioner, Phoenix Force, and Able Team. (It is interesting to note The Executioner’s back story is the same as Marvel Comic’s Punisher and the creator admitted The Punisher is based on him.)
Im thinking of books that I liked so much, I either bought or borrowed as an adult to read again
The Magic Pudding
The Phantom Tollbooth
Moominpappa at Sea (or any moomin story)
Ten days into this thread, can I offer a fourth book? A whimsical re-purposing and classifying of English words, with wonderful prints by Ben Shahn. I loved this as a kid in the 70s, but I think it was first published circa 1960.
I always wanted the Great Brain to be outsmarted (bonus points if it had been by a girl). He struck me as a future robber baron.
Oh man! Excuse me, I have to go do some more Christmas shopping.
- The Egypt Game by Zilpha Keatley Snyder
- The Hero from Otherwhere by Jay Williams (half of the team that wrote the Danny Dunn series)
- All the Three Investigators series (barely edging out Trixie Belden–it’s really a tie, I loved them both)
Honorable mention: The Great Brain series, The Black Stallion series
The Wind in the Willows
A Wrinkle in Time
Chicken Soup with Rice
Ah yeeah 4th book - adored the story
Missed the edit window - deserves more = fantastic book.
Easy-peasy:
The Little Mailman of Bayberry Lane,
Cinnabar, the One O’Clock Fox,
and Ten Beaver Road, which is really more of a YA book, since I read it in fourth or fifth grade.
(In that vein, I must also mention The Mad Scientists’ Club and Project: Genius!)
Swallows and Amazons - Arthur Ransome
The Narnia series - C S Lewis
The Eagle of the Ninth - Rosemary Sutcliff