I bought the PDF of this book this morning, printed it out, and read it during lunch. I think it's actually very good and plan on giving it to my kids to read.

The discussion on number bases and converting from binary, hex, and decimal systems was nicely presented. And the part on endianness might not be necessary at this basic level, but it's nicely done.

Heck, it's a pretty good deal for $3, IMHO.