I need some help. My DS is 6 years old. He's been reading since his 3rd birthday. When he was young he could read for very long periods - he read Harry Potter at aged 4. Around this time he developed ADHD (he also has ASD) and there was a noticable change in his ability to read for long length of time.

He decodes and comprehends at the same level, but we dont know what that is because he's never been tested on levels etc. Its high though. He scored in the 150's on the WJ reading sections.

Now comes my problem - Ive been buying him books that interest him that are digestable as he likes to read the whole book in one sitting, things like small chapter books (my weird school, magic tree house etc) but ive noticed a disinterest of recent times.

Today I bought him one of these books about an adventure in the amazon rainforest because he was interested. On our 5 min drive home he read the entire thing. Thinking that he must have skipped pages (beause it is about 50 pages) and I thought it would be impossible, I asked him about 20 questions from the book and he got all of them correct.

Now I am left stumped and Id love some suggestions. He finds full size novels too much and he loses interest but he told me that he needs books for older kids and I agree.

He loves animals, geography and history. Any non fiction I can buy adult level stuff and he will sit forever and read it. This is only a problrm with fiction.

Any suggestions of good books or how to tackle this would be wonderful!