My sons are now 7,but I could have written your post when they were 6. Honestly, my kids were just more interested in non-fiction at that point, and they still liked pictures and large text.
At age 6, one of them was a very proficient reader of high level non-fiction, but wouldn't read fiction at all at home until we started reading Captain Underpants to him. He started reading it after we would stop for the night, and then he read through the whole series. Next he read the Big Nate series. Some of those are purely comics strips, some are text and graphics. He just moved on to the Diary of a Wimpy Kid series, at age 7. It appears that he is also finally branching out slightly to other fiction books.
My other son almost totally skipped the short chapter books (he read 3 at the end of the school year) and went right to Diary of a Wimpy Kid.
None of this is great literature, I know. But it is great to see them so excited about reading a fiction book. Both love to read non-fiction, but it is important that they also read fiction as that is what the school reading tests use.
