alan ducasse grand livre de cuisine superb
heston blumethal the fat duck cookbook
nobu now
I randomly brought Simply Mediterranean by Byron Ayanoglu and Algis Kemezys off a clearance rack and have used it more than almost any other book in my collection. The recipes are fairly easy and delicious. It looks like it's out of print, but Amazon has used copies available.
I also still love the various Farmhouse cookbooks by Susan Herrmann Loomis. I refer to the French and Italian versions often enough that they live on my kitchen counter rather in my bookcase. Ditto Gourmet's 5 Ingredient which is my husband's go-to book. That book has the best (easy) version of quiche lorraine. I've modified all my quiche recipes using its custard base.
Less a cookbook than an ecyclopedia, Brilliant Food Tips and Cooking Tricks by David Joachim also lives on my counter.
And I live and die by the website Smitten Kitchen. I can't wait for her cookbook. Every one of her recipes works me and leads me in new directions.