Though not likely to be a high-interest book selected for recreational reading, this may fit a curriculum niche.  It describes how levers work and compares different types, always connecting them to real-life tools with which kids will be familiar, such as a shovel, scissors, teeter-totter, nut-cracker, and baseball bat.  The text is simply stated, to make concepts understandable to beginning readers, and well-supported by photos and labeled diagrams.  Besides being useful in science instruction, it also includes typical non-fiction text features such as glossary (with words bolded in the body of the text), index, and table of contents.  Sturdy binding.