The Iron Curtain, that black line that slices the map of Germany in two, is a fact of life - a matter of geography that I, for one, have been able to accept with my head but never with my imagination. Now Anthony Bailey, with his Along the Edge of the Forest (Random House, $15.95), has brought it very close to home , giving me a feeling of what it must be like to be German, living on the brink of the frontier where old familiar roads end abruptly, cutting off families and friends, dividing producers from their markets.
Anyone who has read Anthony Bailey's delightful account of his evacuation from wartime Britain, ''America, Lost and Found,'' will remember that he grew up during the war, when Germans were considered to be the enemy. Then, he says, ''when the earlier feelings of animosity faded - in the way that they did for most people in Europe, as an older generation of Germans passed away . . . I was left with the vacuum of my own ignorance, which I felt needed to be filled.''
So, what with that vacuum to be filled, Mr. Bailey started off on ''An Iron Curtain Journey.'' He took along a driving curiosity about the effects ''of living close to what might almost seem to be a geological fault line.''
After all, this hideous border is, as he says, ''in its perverse way one of the wonders of the modern world.''
He piled his books, clothes, an umbrella, and two pairs of boots into his Saab station wagon and, starting at the Baltic end of the curtain, followed it through Germany (with a side trip into East and West Berlin), Austria, and Yugoslavia to Trieste at its southernmost tip. He had hoped to make occasional sorties through the curtain into the East, but his requests for visas were never answered.
He describes conversations with Germans (residents from the West, visitors from the East) and official tours with border guards (on the Western side), and he relates some of the history of the curtain, proving himself an excellent teacher. He tells of daring escapes from East to West, involving skin diving, ballooning, and, in the case of some Romanians, hiding in a carload of chicken feathers. He gives us a traveler's glimpse of landscapes and villages. ''Here,'' he says of Lubeck, ''is a medieval city of close-packed merchant houses with high gables, tall church towers and spires, and narrow streets, set on an oval island encircled as with mirrors by the calm Trave.''
But best of all he tells how individual Germans feel about the curtain. (Sometimes he has thought it wise to change their names.)
He meets, for instance, Bernhardt Fischer, a man who decided (''it was almost like a religious conversion'') that West Germans must do all they can to foster friendship across the divide to maintain a sense of ''one Germany.'' So Fischer asked fellow townsmen for names of East Germans who would be willing to invite him to visit and put up with all the necessary form filling. Traveling across is far from easy for any visitor from the West. Passing through the checkpoint into East Germany can be harassing, and a technical slip-up can mean arrest. Regulations seem deliberately arbitrary (yes, a canary can go through; no, a Siamese cat cannot) and take as long as 90 anxious minutes. (''It is very well organized, thorough, and depressing.'')
But Bernhardt does it - often - taking slides and photographs and books with him to keep his East German friends in touch with their fellow countrymen. It is worth it, Bernhardt believes. He encourages other West Germans to follow his example: ''Private person talking to private person. That is the most important thing,'' he says.
His efforts are a drop in the bucket, of course. Author Bailey points out that ''in both countries, people allude to each other as druben (over there).'' As for West German officialdom, they strive to make oneness come alive with, for instance, a sign indicating the land beyond the border and announcing ''Hier ist Deutschland nicht zu Endem!'' (''Here also is the fatherland!'').
But of all the stories Mr. Bailey has to tell and all the reactions that he records, one unexpected sight brings the fact of the Iron Curtain home to him:
''It was a sparkling afternoon. On the far side of the river the water was high against the green banks. Beyond was the red-tiled roof of a farm. . . . A watchtower stood close by the farm, and between farm and the river ran the fence. I had already had several reactions to the fence. I had been curious; I had been amazed; I had been horrified; now - suddenly - in this place of great beauty, I felt furious. To live in that farm and not to be able to walk down to the water that lapped against the riverbank! Not to be able to paddle or fish or skip a stone or push out a rowing boat, or sit with one's feet at the water's edge!''
So that's what it means to live with an Iron Curtain.