The Imagaination Station series by Focus on the Family is a good alternative. I’ve reviewed several of the books on my blog. Here is the review for Attack on the Arena.
You orginnaly asked if there was any merit to reading this series. Merit is “the quality of being particularly good or worthy, esp. so as to deserve praise or reward.” No, there is probabaly not a lot merit to reading the books. They are not particularily praiseworthy.
I think the dilemna that we face with is the lack quality literature at this reading level. Yes, there are some, but just not a ton. They want to read and we want them to read. Do you compromise and give them twaddle (even the Imagination Station is twaddlish)? Or do you offer them less selection and encourage them to re-read the good books and strive to improve their reading level? Everyone will answer those questions differently.