Encyclopaedia Britannica Interactive Science Book: Earth

This is good enough for kids from grade 5 to 8 science curriculum.It is not worth to buy NEW one and pay another $19.99 for the SD-X Reader (Reading Pen) which just good for it and the rest of 5 books.USED books are good enough for kids instead of pay $40 - $60 for the new whole set (including reading pen), I only paid about $24 (including shipping cost)for 6 used books, the whole series.I am happy what I paid, what I get.