My latest find for connecting to the curriculum is National Geographic Easy Reader books. I've been using the animal books to get the big ideas of habitat, predator and prey across to my second graders for the past few weeks. There are also other non-fiction titles that would connect well to other units. I've been using the books with my second graders, and lower third graders. I don't have any first graders right now, but would also use the books with that grade level.
I love these books. My kids are very interested in the different animal pictures (and they are great ones) and learning about non-fiction in general. I also can get some great non-fiction comprehension questions as well as practice working on inference skills throughout the books. One of my biggest inference areas is when the author talks about what certain animals like, we make inferences about what they don't like. The books also have great vocabulary for targeted areas. My second graders are learning about animals right now and some of their key words are habitat, predator and prey. The key vocabulary words are highlighted in the text with a pop out word + definition, and then reviewed at the end of the book. I really like this, since as we all know, our students need so many more times hearing and seeing a word to learn it.
I've found that both levels 1 and 2 are great for single speech session lessons, while level 3 books usually take 2 days with some review time on the second day. I also don't read the books word for word, after a few trips through, I'm paraphrasing. I skip over some parts and spend lots of extra time on other parts.