Who says television is not intellectually stimulating? Watch long enough, and you`re bound to find something to think about.

Speaking of which, ''The Love Boat'' is gone, but Vanna endures.

''Boat,'' in fact, was barely canceled this time last year when ''Wheel of Fortune`s'' Vanna White developed into a phenomenon worthy of at least a half- formed thought or two.

Like everything on television except Bill Moyers and some wildlife specials, Vanna`s significance is accidental. Her charm is that nobody knows this better than she. Vanna did not set out to make us think; why, she barely thought herself! Her mission was merely to decorate the flabbier lobes of our brain for a while and take our minds off the national debt.

But the ozone grew thinner, Capt. Stubing retired, and Vanna was kicked upstairs. As a major cultural symbol, she is clearly out of her league. But she`s a good sport about it.

To help us understand her, and to make some hay before her season is over, Vanna has produced ''Vanna Speaks'' (Warner, $15.95), currently nearing the top 10 on the New York Times best-seller list.

Not `Uncle Vanya`

Reading ''Vanna Speaks'' is not like reading ''Uncle Vanya,'' but it`s no ''Goodnight, Moon,'' either. When you`re finished--in two hours, barring heavy turbulence--you have that bloated feeling that says: Information has been absorbed.

The major points of ''Vanna Speaks''--that Vanna hates her toes, that Vanna`s fiance died in a plane crash last year, that Vanna loves her job but knows it`s not brain surgery--have been widely publicized already, minnows tossed to an anxious public. More Vanna-bait:

-- Vanna wears a perfect size 5, but was once capable of eating an entire cheesecake in a sitting.

-- Vanna`s favorite magazine is Architectural Digest, and she waters her houseplants with the water in which eggs have been boiled: more nutritious.

-- As a young modeling student in Atlanta, Vanna once smoked pot and then ate an entire meat loaf, an experience that became a cornerstone of her present anti-drug stance.

Between the lines, there is even more information. Vanna`s been around. She`s lived with two men, modeled lingerie racy enough for the photos to wind up in Playboy. Early in her struggling-actress days, her ''mentor,''

Christopher George, felt the need to tell her, ''Vanna, you can`t get a job in this town lying on your back.''

Bimbodom beckons

Unafraid, yet blessed with the good sense of a survivor, Vanna embraced the bimbo way of life. Reading this, you think: If there were no Vanna, we wouldn`t have to make her up; we`d still have Donna Rice.

Reading Vanna`s book is a perfect antidote to watching Vanna`s show.

''Vanna Speaks'' will load your noggin with factoids, but ''Wheel of Fortune'' will throw open the windows and let in some air.

Solving ''Wheel`s'' puzzle requires that you divulge information, but gives you none in return; it`s a question without much of an answer. Half an hour of ''Wheel'' leaves you blank and giddy, relieved of vowels and consonants, empty-headed and thus perfectly prepared for prime time.

That makes Vanna our national television hostess, and that`s something to think about. --