What does he like?
What sort of reading ability?
There's so much! DS is year 3 and DD reception, so I'm including some that DS didn't discover till later than year 1 but DD also loves.
Lots of picture books still - Dr Seuss, Julia Donaldson, Hairy Maclary et al (fantastic vocabulary in some of these), Winnie the Witch, Thomas the Tank Engine.
Pirates were in. Jeremy Strong Pirate School and various Frank Rodgers including Pirate Penguins. Captain Abdul's Little Treasure (loooong picture book, very funny). The Indoor Pirates by Jeremy Strong is good too.
Anything Jeremy Strong is popular here really. We like a bit of humour. My Dad Has an Alligator and Hundred Mile an Hour Dog are longer/less pictures but also very much loved.
Dinosaur Cove were DS' first chapter books to read to himself in year 1. I found them a bit formulaic.
The Owl who was afraid of the dark (chapter book incarnation) & series was a big obsession, very sweet.
A recent discovery which both DC are loving is Mr Gum. Completely bonkers but has them both in stitches.
Long time favourites for parent-read bedtime stories were (are!) Just So Stories and Winnie the Pooh.