I don't really like ebooks for my cookbooks, but if I had just 10 books, I'd maybe select these:
Long Nights and Log Fires: Warming Comfort Food for Family and Friends
Plenty: Vibrant Vegetable Recipes from London's Ottolenghi
Better Home and Gardens New Cook Book (1989)
Simply Sensational Cookies: Bright Fresh Flavors, Natural Colors & Easy Streamlined Techniques
Roast Figs, Sugar Snow: Winter Food to Warm the Soul
The Country Cooking of France by Anne Willan
The Complete Asian Cookbook by Charmaine Solomon
The Art of Simple Food: Notes, Lessons, and Recipes from a Delicious Revolution
Blue Willow Inn Bible of Southern Cooking