Summer is here and, with it, the prospect of vacation. People are already packing: passports, bathing suits, cameras . . . and books. Not many leave without at least one paperback stuffed into their bags, if only out of a vague sense that books are to August as rain is to July -- a defining element. Some lug along entire mini-libraries and consider it a point of honor to finish the lot before heading home.

There are two main theories about summer reading, just as there are two main theories about the purpose of vacations. Some people hold that the point of a holiday is to relax, i.e. do nothing. These are the folks you find sitting decoratively around the pool or hot spring or on the beach, alternately snoozing, reading and sipping more gaudy drinks than are good for them. Mental rejuvenation, according to this view, requires switching off, kicking back and giving the synapses a thorough rest.

Others concur on the goal -- relaxation -- but maintain that the way to achieve it is to get blissfully, physically exhausted. These people don't sit or lie on the beach; they run on it. They don't take ocean cruises; they surf and jet-ski and snorkel. They ride horses and play golf and climb mountains and take aerobics classes. They sight-see, avidly, inquiring endlessly about the history, geography, customs, flora and fauna of their holiday destinations. A vacation to them is part workout, part social-studies class. At the end of the day, one would think, they are too tired to read anything but the dinner menu, but being the driven types they are, they squeeze it in somehow.