My 4.5 year old is enjoying the Narnia series. It was read to me at the same age, and I remember it fondly, and understood most of it.
They probably ARE a bit beyond him in some ways but that’s okay- hearing the more advanced words and experiencing longer form narrative doesn’t hurt, and if you have the patience (which I’ll be honest, I don’t always at bedtime), can spark interesting conversations “what’s a centaur? Is Caravel (Cair Paravel!) a real place? Is Narnia before or after the dinosaurs?” Etc etc.
We only read a few pages at a time, and it’s a lovely thing to know he’s reading the same copies I did, at the same age.
We also read the Little Prince- which he didn’t understand at all, but enjoyed the illustrations and the rhythm of the story.
We DO also read more age relevant stuff- so it’s not all “push push” - we like Oi Frog, Dinosaur that Pooped..., We Found a Hat, usborne Greek myths collections, dinosaur encyclopaedias, non fiction books about poo, space, the environment, Hairy McLairy, Spider-Man comics, Mr Men, ... I strongly feel that introducing as broad a range of texts (including some that stretch kids quite far) is very very necessary to avoid kids “pigeonholing” themselves as readers down the line.
I do read The Large Family books but I find them quite outmoded in attitudes to women, diets, division of domestic labour etc. so don’t love them personally.