You need a book for a child, and you don't know what they read, how well they read, or what's already on their shelf. So stop trying to guess. The whole trick is picking something that survives being wrong. Two of these are performance books, where the grown-up does all the work and your child only has to sit and watch — those land even if they can't read a word. Three are fact books that a seven-year-old and an eleven-year-old both browse happily, so you can't pitch them too young or too old. Pick one and you're done. And each one tells you straight whether it's likely already sitting on their shelf, because that's the failure you're actually most likely to hit.
Eight books; pick one and stop. When you don't know the child, sort by what survives you being wrong, and this shelf falls into three piles. THE PERFORMANCE BOOKS, which are the safest thing here: 'The Book with No Pictures' and 'The Wonky Donkey' both hand the entire job to the adult holding them. The words force whoever is reading to say something ridiculous, and your child sits there and watches a grown-up lose. That means the gift works at three and at seven, for a fluent reader and for one who can't read at all, because reading is not the thing being asked of them. Almost nothing else in a bookshop is that forgiving. THE AGE-PROOF PILE: 'Weird But True!', the almanac and the records book are one fact per page with a photograph, so there's no age to be wrong about. A seven-year-old and an eleven-year-old browse them the same way, and no child has ever opened a fact book and felt it was beneath them. That's the hedge when the only thing you know is roughly how tall they are. THE ONES THAT NEED YOU TO KNOW SOMETHING: 'We Don't Eat Our Classmates' and 'The Gruffalo' need the age to be about right, and 'The Adventures of Captain Underpants' needs the family to be fine with it. Now the part nobody warns you about, which is duplication. 'The Gruffalo' and 'The Book with No Pictures' are two of the most-owned children's books on earth and 'The Wonky Donkey' went viral in 2018 and sold in the millions on the back of it — assume all three are already on the shelf unless you have reason to think otherwise. The safe bets are 'We Don't Eat Our Classmates', which is loved but nothing like as ubiquitous, and the three fact books, where a duplicate barely counts as one: the annuals change every year, and 'Weird But True!' is a cheap pocket paperback that a fact-hungry child is happy to own twice and leave in two different bags. Last, the thing that actually rescues this whole problem. Write in it. When you hardly know a child, the inscription is the only part of the gift that's from you rather than from a shop, and it's the only reason a duplicate still beats no gift. Don't write 'Happy Birthday, love from Sarah'. Write the date, and one specific true thing — where you met them, something they said that you remember, or what you hope they make of it. The note under each book says what to write in that one.