These are two of every year's guaranteed fun categories: children's picture books and Young Adult novels – when either is done well, without schmaltz or condescension, they become immediately enjoyable to readers of all ages. And it's surely a healthy sign that so many first-rate books in either category are published every year that winnowing things down to one discreet list of the best is nearly impossible – but here is that list: 

10 Let’s Go Swimming on Doomsday by Natalie Anderson (Putnam) – We start our list this year with a case-in-point: a YA novel so good it might easily have been the #1 choice in less-contented years. Natalie Anderson's story of young Abdi – forced to become a child soldier in a fanatical militia, forced into a suicide mission he only barely survives, becomes one of those characters readers just clutch onto, hoping that somehow they'll reach daylight.

9 The Line Tender by Kate Allen (Dutton) – In this incredibly heartfelt story, young Lucy Everhart is only seven when her marine-biologist mother suddenly dies, and from that moment on, Lucy is trying desperately to hold the rest of her life together and still pursue her mother's research into great white shark migrations off Cape Cod. Lucy is a masterful fictional creation, and there isn't a reader in the world who won't be rooting for Lucy to find peace at last. 

8 Romeosaurus and Juliet Rex by Mo O’Hara, illustrated by Andrew Joyner (HarperCollins) – If only Shakespeare had had the genius to tell the tale of his star-crossed lovers in dinosaur form! This story of two young sauropods from opposing clans (or is it clades?) who just want to love each other is, as even that brief description should make clear, utterly sublime.

7 The Good Egg by Jory John, illustrated by Peter Oswald (HarperCollins) – The Good Egg in question will be well-known to every reader of this fantastic book: they're that one person who makes a point of always smiling, of always being cheerful, of always having, you'll pardon the expression, a sunny-side-up disposition. And the lesson learned is a valuable one: even Good Eggs occasionally need to relax and look after themselves a bit.

6 Bach to the Rescue!!!  by Jose Angelberger, illustrated Chris Eliopolous (Abrams) – The origin story of JS Bach's Goldberg Variations has never been told quite like this before: Angelberger's funny scripting and Elio's antic pictures combine to make it a touching and hilarious musical adventure.

5 Ten Rules of a Birthday Wish by Beth Ferry, illustrated by Tom Lichtenheld (Putnam) – In this beautifully-drawn little fable, a cast of animals gathers in order to establish the rules for making a birthday wish, and the result is a book that's pure gold to read aloud when a child (of any age) is having their Big Day.

4 Lost and Found by Orson Scott Card (Blackstone) – Orson Scott Card has always excelled in writing about young men who are figuratively and sometimes literally outcasts set apart from their peers, and in this YA novel he delivers just such a tale, only without spaceships or no-go plows. Instead, we get this sensitive and hugely empathetic story of Ezekiel Blast, a young man with a knack for finding lost things – and who's a little lost himself. 

3 The Infinite Noise by Lauren Shippen (Tor Teen) – Lauren Shippen's winning debut novel is doubly unlikely: it's based on a podcast and yet not derivative and in-crowdy, and it's a gay first-love romance set in a high school and yet not syrupy. Instead, this story about a young football star with the ability to feel the emotions of everybody around him – and his meeting with a boy who makes him think this might be a blessing instead of a curse – is smart and funny and moving.

2 Field Trip to the Moon by John Hare (Margaret Ferguson Books) & Armstrong by Torben Kuhlmann (North/South Books) – 2019 was the 50th anniversary of the Apollo moon landings, and that was reflected in a solid dozen genres in the course of the year. Two of the best of the items in question were both kids books: a wonderfully whimsical story of an eventful lunar field trip, and a whimsical-yet-genuinely-touching story of the little mouse who makes it to the moon ahead of any human.

1 The Light at the Bottom of the World London Shah (Disney-Hyperion) – London Shah's debut fantasy novel, the best YA novel of the year, is a remarkably assured vision of a world in which rising waters have inundated so much of London that humans have migrated under the waves. The story Shah tells is so full of wisdom and adventure that it easily wins the top spot.