That's actually a far more difficult question than it seems. I've got three books on "Mediterranean Cooking" and I wouldn't honestly recommend any of them. One is too brief; the second is , well, ok, and the third is a huge tome (800 pages) full of recipes, boring as hell and the most appalling organisation I've ever seen.
Mediterranean cuisine covers Spain, France, Morroco, Algeria, Libya, Egypt, Lebanon, Greece, Turkey, Croatia,wow, more than 20 countries in all with 20 different cuisines. To slap them all together and say "Yeah! I've nailed it!", is never going to happen, but there are certain things that stick in my mind (and I've probably omitted another thousand).
Fresh ingredients, and I'd mention tomatoes, courgettes, peppers, aubergines, onions, garlic, cucumbers, anchovies, olives, capers, just to start. Lots of fresh fish, usually prepared very simply. olive oil. Delicious bread, often flatbread. Fresh herbs. Yoghurt. Grilled food.
I looked on Amazon and on a few other websites for "Mediterranean" cookbooks, and one that stood out was "The Complete Mediterranean Cookbook". I like what they offer and it reflects what I've eaten in France, Spain, Italy, Greece - and my local Lebanese and Turkish restaurants! I have NOT read the book completely, but I might just ask Santa to do me a favour...