The Boxcar Children series, by Gertrude Chandler Warner, I don't know how to rate them because they're a series!

   Going to try out my new way of writing about books! Let's see how it goes...
   This is a series about four children, Henry, Jessie, Violet, and Benny, who go everywhere to find a mystery (or rather, a mystery finds them everywhere). Many different stories, many mysteries, many ways of solving enigmas.
   I read the entire series in first grade (Here's a link to the entire series. I read all of the regular ones, and most of the specials), though I don't think that an average first-grader would have read those as easily as I did. They're more of a third grade reading level. And I haven't heard of any movies about this series, but I'm sure there's some floating around. Oh! And my favorite one is the third one, The Yellow House Mystery. Another good one is the twelfth, Houseboat Mystery. But make sure you read them in order, because sometimes they talk about things in a book that were in previous books and you might not understand if you didn't read them in order.
   Books 1-19 were written by  Gertrude Chandler Warner. The other books, I'm not sure.