I married a map reader.

At 6:30 p.m. he trudges through the door, tugging at his tie and loosening his belt. He peels off his socks and shoes, drops into his overstuffed chair -- which sends stuffing snorting out the sides -- and reaches for entertainment.

What he lays his hands on isn't a paperback novel or the TV guide. It's not even his wife. My husband reaches for his Rand-McNally Road Atlas. And apparently so do a lot of other people. The 1981 edition was on the Publishers' Weekly Best Seller list for 34 weeks.

This peculiar pleasure of my husband's shouldn't have taken me by surprise. I also have known him to become engrossed in telephone books, dictionaries and the "For Sale -- Miscellaneous" classified column. But never having read a road atlas for any longer than it took me to find the exit number off the New Jersey Turnpike, I failed to understand how he could hunch over it for an hour.

My husband is an intelligent man, the common-sensical sort. Practical. Efficient. He likes to know how and why things work. He dissected tractor engines and lawn mowers as a boy on a Midwestern farm. So I was sure that while he pored over the atlas he was gleaning from those veined and dyed displays of Minnesota, Arizona and Vermont some surgeon's insight into the physiology of American society.

Hadn't I heard him--when asked "What is so-and-so like?"--reply, "Well, she's from Alton, Illinois," and then reach for his Rand-McNally and pinpoint that city in south central Illinois. After studying the state's two-page spread for a few minutes, he seemed to know just what to expect from the Alton native: her general attitudes toward politics, religion and her social life. It seemed to me that by spreading out the whole of the United States and Canada on his lap he was, like God, getting a glimpse of us from above. The two of them knew where everyone fit.

I noticed myself becoming a little edgy, evasive in my own home. Was it my imagination, or was he studying with great care that little bulge of wooded land in northwestern Michigan where I was born and raised?

Enough! It was like living with a Sigmund Freud of the States. If there were to be any trust in our marriage he'd have to share the secret of his geographical psychoanalyses.

I prepared to ask the question when a whole evening stretched before us, so that he could carefully elaborate and explain to me the social-psychological constructs he deduced from map reading. I began at dinner:

"Doug, why do you read maps?"

His answer took about three seconds. "Because I like to know where things are." Caught between bites of cauliflower, he didn't even have time to mince his answer. It came up whole -- the mystery of his map reading in eight words.

But with some pumping and prodding, I got him to say a little more, such as:

* "The question people ask you most often is, 'Where is that?' And I like to know so that I can tell them where to go."

* "I like to know where I'm going too. I like to be able to stick down my finger and say, 'That's where I am and that's where I'm going.' "

* "But even if I'm not going there, when I hear about a place on the news or in a conversation I like to be able to picture where it is. It keeps me from asking some stupid questions. Say it's December and you hear on the news, 'It was 50 degrees in Juneau, Alaska, today.' People gasp and say, 'How could it be so warm in Alaska?' like it belongs in 'Ripley's Believe It or Not.' But if they'd just look at a map, they'd see that Juneau is only 450 miles north of Seattle -- it's not Nome, on the edge of the Arctic Circle or anything -- and that makes 50 degrees in Juneau in December perfectly reasonable."

I have concluded that map reading is largely a pleasure in itself -- like putting together a jigsaw puzzle -- and does not represent some primordial quest for omniscience or domination of one's world.

There must be thousands of people out there who enjoy map reading for map reading's sake. The Rand-McNally Company reports that last year's atlas first appeared on the Publisher's Weekly Best Seller list the first week in February. That is well before vacation season and a utilitarian value -- say, mapping the shortest distance between Detroit and Denver. The 1982 Rand-McNally Road Atlas ($5.95) is just out; other people must be spending whole evenings exclaiming things like, "So that's where Keokuk, Iowa, is!"

It has happened in our own home. When I first became aware of what I thought was a curious quirk, I mentioned it to two guests as a conversation starter. "Do you know what this crazy man I married does? He reads the Rand-McNally Road Atlas -- for fun!"

It started conversation all right. But instead of the good-natured hoots I expected, our guests sat up in recognition and nodded their approval. "We do too!" Out came the Rand-McNally, and the rest of them -- my husband and our guests -- clustered around. I was left on the edge of their inner circle, shaking my head while they ranged far and wide:

"Do you know where Manhatten, Montana, is?"

"Look, it's here, near Bozeman."

"Well that's not far from Jackson, Wyoming."

"I once knew a girl from Manhatten, Montana."

Through the Rocky Mountain States to the Pacific Northwest, from the Redwood Forests to the Gulf Stream Waters: 12 states per hour. When I could see that it would be well past midnight before they arrived back in Washington, I sat down to re-read my seed catalogs.