A lot of the ones I'm keeping are single-subject books, and narrow the focus in some way.
Having grown accustomed to Google searches for say, salad, and finding multiple options, I grow increasingly frustrated with books that have 1 or 2 recipes, then move on to the next topic. While I like Ina Garten's books, she's a good example of the style I've grown increasingly frustrated with. (I'm keeping her books because I know them so well, but it's the style/format I'm no longer interested in.)
For instance, I'm keeping single subject books on Bread, Ice Cream, Baking (in general), etc. and also diving into ethnic foods: Vietnamese, Mexican, Spain, Middle Eastern, etc.
I have a whole book on tamales and I love it. It covers not just Mexican tamales but touches on Central America and the Caribbean.
Naomi Duguid's books are another example. While I loathe the coffee table format in many of her books, I love the focus on a specific region or style. And her recipes aren't just good, they're incredible.