"Christmas Style" is rather unusual for a Christmas decorating book. (And as a librarian, I've seen tons of them!)
The first 2/3 of the book could be called "Christmas themes". Each 2-page spread shows a different theme. Each theme features pics of a lovely tree demonstrating that theme. Surrounding this, there are smaller pics of supporting decorations - centerpieces, mantle swags, oranments, etc. - that support the theme. The themes are sometimes classic ("country warmth"), sometimes sophisticated (like the "decadent design" theme which features black and silver), and sometimes whimsical (like the themes based around silver screen movie actresses). Many are unusual. All are well done and inspiring.
The last third of the book covers practical things - selecting real and artificial trees, tree setup, lighting, using ribbons, bows and fabric as decoration, how to hang garland, types of ornaments, tree toppers, etc. (the list goes on).
This book has a great combination of inspiration combined with practical advice.