There are books that I buy for cooking and there are others that I buy for viewing. As I develop my culinary skill I find that I need fewer pictures but I still enjoy them. There are so many cookbooks at the bookstore these days that inevitably your eye will be drawn to beautiful covers. So even though I might pick up a pretty cover first I'll probably buy the one that has better recipes.
I like books with lots of info about ingredients: how to chose them,where they are from, techniques, variations, menu suggestions etc. That's why to this day I still consult with Julia Child regularly. SHe has tons of pictures in her books but they aren't just pretty pictures, they are useful pictures. I also like the Dean & Deluca book for thorough info.
As for books for pleasure, I love Lorenza DeMedici's books. Her books are minimalistic on the recipe side but have lavish photos of Italy: the countryside, beautiful mansions, exquisite menu presentations etc. To say that I never cooked with her books would be a lie: she taught me how to make a proper risotto.
I also have a 3rd type in my book collection. Everywhere that I travel I like to pick up at least one cookbook. Most aren't all that useful because you almost always need local ingredients to make the recipes but I love them anyway because they are - in a way - a short history lesson of the region.
Sorry to be so long winded.. ;)