I got the first boxcar children on kindle for my ds5.5 to read. He can read it but it is ds3.5 who likes it. Ds5.5 would rather struggle through zac powers or have me read famous five or the sassafras zoology book.

you could try Horrid Henry or the Secret Seven. Lots of kids seem to like Geronimo Stilton too. I liked Jennings and Darbyshire too if you can get them (they are 50's books).