I've read before this figure that a reading book should be about 90 to 95% readable without support by a child.
Ds is in reception and his last few books seem like maybe they were too easy. They were maybe 300 words and read it all fluently with only 1 word he had to sound out and 1 other word he guessed wrongly and I had to correct him on.
Does that sound too easy (assuming it's not been given to him to work on his comprehension or expression which I don't think is the case)?