While it's been tough to find good books that sustain the compare and contrast text structure, I've found some great problem and solution books. One that is easily available is the title When the Wolves Returned.
Why do I like this book? Like many recent nonfiction books, it's written on two levels. Simple text is included in white boxes, while the author goes into more detail in a longer paragraph. This two level readability makes it a good fit for most classrooms.
I also like the way that the author interweaves causal relationships within the problem/solution structure. This is the way that text usually works. Problems don't just appear overnight; they have causes. The relationship between the causes and effects--and how they fit with the problem and solution--are very clear in this book.
The first half of the book explains how wolves were eliminated from Yellowstone, and the effects of this elimination. This is the problem. Then, in the second half of the book, the author describes how bringing back the wolves has been a solution to the problem. Of course, to show how the return of the wolves is a solution, the author needs to explain the effects of the wolves' return.
I can see this book working well as an introduction to the text structure of problem and solution. Even better, the endpages show an interconnected web of animal photos, with a caption inviting the reader to recall the effects that the wolves' return has had on each species. Pretty neat!