Hmmm. How about some of Judy Bloom's books for younger readers? The Fudge books or Otherwise Known as Sheila the Great? I remember The 100 Dresses by Eleanor Estes being quite short and an easy read, as well. The American Girls historical series are surprisingly well written. These all might be slightly more difficult than Magic Treehouse or the Rainbow Magic Fairies.
Cynthia Rylant's Cobble Street Cousins series is very, very easy, but fairly well written -- they might be a little dull for a fifth-grader, though. Other easy-reader series that my daughter liked were Dragon Slayers Academy and A to Z Mysteries. I can't say either series is great lit, but definitely a cut above Magic Treehouse. Oh, and she loved the Katie Kazoo series of early chapter books. Those would appeal to an older kid pretty well, I think -- Katie magically switches places with other people and animals, and the books are pretty decent for an early-reader series.
Cynthia Rylant's Cobble Street Cousins series is very, very easy, but fairly well written -- they might be a little dull for a fifth-grader, though. Other easy-reader series that my daughter liked were Dragon Slayers Academy and A to Z Mysteries. I can't say either series is great lit, but definitely a cut above Magic Treehouse. Oh, and she loved the Katie Kazoo series of early chapter books. Those would appeal to an older kid pretty well, I think -- Katie magically switches places with other people and animals, and the books are pretty decent for an early-reader series.