I frequently facilitate grade 3-5 math workshops for teachers. Whenever we discuss decimals I always mention the book

Little Numbers and Pictures That Show Just How Little They Are! I think it's a nice book to use with 3rd-5th grade students because:

1. The "unit" is a dinosaur. Specifically, a seismosaurus. Kids need to understand that a "unit" can be flexible. In this book, everything is measured in terms of a dinosaur unit.

2. The book depicts increasingly smaller measurements. If a dinosaur is worth 1, then a dinosaur shrunk to 1/10 will fit in the front yard. It talks about various other tenths, like a dime being a tenth of a dollar. It shows both decimals and the fraction equivalent.

3. The numbers creatively get smaller, each time decreasing by powers of ten. For example... 1/10,000 is an ant. 1/1,000,000 is an amoeba. Some kids will be very intrigued by the exponents, which are also included.

4. The book is big (13 x 8") and good with crowds.

If you teach decimals or fractions, I recommend it!