Sardinia's Emerald coast

Only on the Costa Smeralda, the Aga Khan's pricey Sardinian resort, would you find Nietzsche, Kafka, Strindberg, and Kierkegaard in a little piazza bookshop. I made this discovery my first morning on the post, so by the third evening I was not at all surprised to find a set of the Encyclopaedia Britannica in the Hotel Cervo's lounge.

It was nearing dusk and the piazza was filling up with beautiful people - bella gente, they are called in Italy - strolling about in their blousy cotton T-shirts and well-tailored Bermuda shorts. I was beginning to wonder what the real Sardinia - the Sardinia beyond this 30-mile summer dreamland - was all about, so I reached for the Britannica. This is roughly what I copied down:

''Second-largest Mediterranean island; 9,301 square miles; 71/2 miles from Corsica across the Strait of Bonifacio; 115 miles north of the African coast. Highest mountains are 6,000 feet. Has climatic characteristics of northwesterly mistrals and hot southern sirocco. Myrtle, rosemary, thyme, are plentiful. Dwarf palms in parts. Cork oak in interior.''

Now you know more about Sardinia than does the average visitor to the Costa Smeralda (Emerald Coast), as gorgeous and sequestered a strip of resort turf as I've found. True, there are Sards working for the Aga Khan's consortium, there are Sard folk dances once or twice a week in the Porto Cervo piazza, and there are Sard dishes - someone told me they can do a dozen things with eggplant - at the poolside buffets.

Overall, though, the feeling is cool and continental, probably a reflection of the Aga Khan himself, who is known by consortium staff members as ''H. H.,'' for His Highness. He is spiritual leader of the Ismaili Muslims, a sportsman, and an entrepreneur who despite his wealth and station drives around the coast in a black VW beetle and cuts a rather informal figure, in blazer and white slacks, at the sumptuous outdoor buffets he gives for visiting motor-yacht ralliers. He was more than accessible at the one ''do'' I attended, but the talk around him was mostly of boats, so I listened and nodded and watched a million-dollar dusk settle about him.

Twenty years ago this craggy northeast coast was wild, almost uninhabited. Then the Aga Khan set to work hiring Europe's best architects and designers who, adhering to strict building codes, sculpted a series of harbors, piazzas, and hotels that look almost medieval in their irregular pink-stone grace.

There are nine hotels on the Costa Smeralda, ranging from small and chic to smaller and chic. You can spend as much as $220 a day for two (demi-pension) at the Cala di Volpe or the tiny Pitrizza, which juts bunkerlike out of a seaside cliff, or half as much at the hilltop Genestre and the Luci di la Muntagna, above the $500,000 yachts in Porto Cervo Harbor. My pad was something in between , a little Spanish mission of a place called the Hotel Cervo, with crooked sloping hallways leading away from a flowery inner courtyard.

What to do on the Emerald Coast? I would answer that, but I didn't see enough of my fellow tourists during the day to know exactly how they disported themselves. This is the Costa Smeralda disappearing act, which the Europeans have so long mastered. By 6 o'clock they always materialized in the piazzas in their Bermudas and T-shirts. I do know where I went. I scouted some of the 80 -odd beaches tucked into the coast (though I found the prevailing mistral made it almost too cool for swimming); jogged on the lovely Pevero Golf Club, an 18 -hole Robert Trent Jones course, sniffing rosemary and thyme from the rough; sped up and down the coast in a Magnum Marine yacht which was as well tooled as a Rolls-Royce; took a far humbler rented Chris-Craft out for a picnic spin to the offshore island of Mortorio, where needle-nosed yachts lay about like battleship row at Pearl Harbor.

This was not the Sardinia that D. H. Lawrence saw when he tramped the rugged interior of the island in the early 1920s, a trip he recorded in ''Sea and Sardinia,'' which begins with the irresistible line, ''Comes over one the absolute necessity to move.'' Lawrence might as well have been exploring the remoter reaches of Ireland or Scotland, for he found the Sards dour and unaffected, the landscapes sprawling and Celtic.

On my fourth day I finally went looking for the real Sardinia, accompanied by a member of His Highness's staff, Anna Sacripanti by name, who I think welcomed the excuse to get off the glorious compound. We drove to the port town of Palau, passing through sheep country broken up by stone fences, then pinnacled gorges that reminded me of the Dakota Badlands. All across Sardinia the landscape is studded with nuraghes, the ancient cone-shaped stone objects that the Sards once used as shelters, fortresses, or tombs.

At Palau, from which you can make out the island of Corsica, we settled into the buzzing little Trattoria del Sub near the harbor and dispatched mounds of crayfish and rock lobster. ''Sardinians,'' said Anna, ''are tentative and shy until they know you. They have had a long history of being invaded. That is why they lived inland, and the Costa Smeralda was empty when H. H. began to build.''

The waitresses wore crestina, white lacy embroidered Sardinian caps, but the rest of their costume was far from indigenous: white T-shirts and black Bermuda shorts. ''Anna,'' I said, ''the world is growing smaller.''