Books for 8-12yr reading level, but suitable for 5yr old (emotionally & thematically)

Looking for book recommendations that suit 8-12 years reading level, but suits a 5 year old in terms of emotional maturity and themes.

(For a 5yr old who has very advanced reading skills but is very sensitive and otherwise developmentally at 5yrs old). Occasional illustrations are nice but not necessary.

Book series that have been a success:

• Pokemon chapter books
• Toto The Ninja Cat by Dermot O’Leary
• Murray and Bun by Adam Stower
• Rabbit & Bear by Julian Gough 
• Hot Dog by Anh Do
• Sophie Mouse by Poppy Green
• Hotel Flamingo by Alex Milway
• How to Train Your Dragon by Cressida Cowell
• Some Dr Seuss books

Books that were enjoyed once but not enough to re-read:

• Captain Underpants by Dav Pilkey
• The 13-Storey Treehouse by Andy Griffiths and Terry Denton

Books on the shelf that we will try soon:

• The BFG by Roald Dahl
• Animal Ark series (reading with an adult at bedtime because of some sensitive themes)

Books that weren’t a success:

• The Boy Who Grew Dragons by Andy Shepherd (themes were a bit too mature for preschooler)
• Ninja Kid by Anh Do (as above)
• The Enchanted Wood by Enid Blyton (got bored, didn’t finish book)

Thank you in advance!