Appropriate grades or age groups:
Preschool and Younger
Elementary School
Middle School

Other suggestions or comments:
The best way I've found to create "readers" in my family seems to be to allow THEM to choose what they read and they don't always have to "know" they're reading to you! My best example of this is my youngest daughter, who's 8. She isn't a big reader and hates to stumble or feel inept. I tried and tried to find articles and books that would interest her but to no avail. Then one day I thought "What does this kids love the most to think about?" and the answer came quickly to me..... clothes, makeup and girly things. So I picked up the JC Penney's catalog and began discussing what she would like out of there. Next thing you know she's reading to me what that really cool blouse she loves is made out of, what colors it comes in and so on! Then, taking it a step further (why not.. she's already fooled into reading.. hehehehehe) I told her "Well if you had $45 to spend what items would you get?" Next thing you know she's creating a list, adding numbers, reading all about the items to see if they're "worth" the money and having a ball. Hours later she still hasn't realized she not only completed a reading lesson, but a math one too! I know... I'm sneaky... but she's now reading at 3rd grade levels while just finishing 2nd grade when last year at this time we were struggling to accomplish just kindergarden stuff!!!!!
I think the key to any readers success is to find what they love the most and allow them to find all they can to read about it. She also reads Teen Magazine and loves anything "Britney"! Her twin brother does the same but with hockey... the game he lives for! We not only find easy readers on the subject but read hockey cards, hockey magazines, and mom creates hockey "stories" to read about different players. He loves it and suddenly this little man is reading 2 grades higher than he's in also! So keep them interested and they'll do the rest by themselves!