Kathy, sometimes added gluten is necessary if you're baking with 'other' flours. Whole grain flours and non-wheat flours (rice or corn) have little or no gluten so it must be added.
It sounds like the book has a lot more than recipes so it might be useful as a reference tool. $12.00 is not a lot of money for a good cookbook.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan