My son has to read for 15 minutes every night for school, which means finding 5 or so books a week that he can read. Strangely (sarcasm alert), over the past few years of bringing home armload after armload of children's books, we ended up with very few Early Readers, because mostly they are unappealing paperbacks (with exceptions). But anyway, every fortnight or so I run through the shelves looking for candidates for the coming week, working on the assumption that he is making progress, so books too hard in April might be possible now, and perhaps we'll be trying Tolstoy by August. Not that we actually own any Tolstoy. I feel I can always get it from the library if I need to.
This week I found The Happy Hockey Family, by Lane Smith. I love this book. It is brilliant. I have read it aloud to my children often, coaching them in the appreciation of ironic humor (so important). I checked the copy at our library (bought by me using Friends' money; I think it was one of my first acts as an official Friends of the Library Member), and it does not have an "easy reader" sticker on it. But it is. Short, clear sentences, some repetition, illustrations that support the text. It was perfect. Of course, since I had read it aloud to him before, he was probably reading from memory, but that's not my fault.
Lane Smith has a website here that is well worth visiting, but he's taking a break from it until his next book comes out...
For more suggestions of books for a six year old to read, visit Kelly at Big A little a for a nice list.