Mine was 8 (summer after year 3) when she went from being an excellent but extremely reluctant reader to not wanting to stop reading at bedtime.
As others have said, it was just finding the right books (I tried A LOT! 🤣) and I agree, it was more of a struggle when she was younger. Tbh, I would say it's only been the last year (she's just finished year 5) when I feel we're more spoilt for choice and her reading has gone up another notch.
So the first book that "I let" her carry on reading after I'd finished reading to her at bedtime was 'Daisy and the trouble with chocolate'. She devoured the whole series, then moved on to the 'Baby aliens' (Pamela Butchart) series. Both of these series are funny, engaging and very accessible in terms of language and pictures.
In the last two years, she's gone from reading those to reading hundreds of books, from the Harry Potter and Skandar series to Onjali Q Raúf to Lottie Brooks and Tom Gates.
She was greater depth in reading from reception until the middle of year 2, then went down to expected, but as of her year 5 report, has now gone back up to greater depth.
She's got ADHD and dyslexia so sometimes still struggles to initially get into a book (so I often start her off by reading the first chapter).
Her 8-year-old brother is similarly reluctant (and not quite at the reading level DD was) so currently trying to find his gateway books...
Oh and also, for some reason (she's also ASD, so possibly that) DD only ever reads at bedtime, even if she has an ongoing book that she can't put down. So we sometimes go up two hours before to allow her time to read!