There was a short novel I found in my library few years ago, whose title nor author I don't remember. It was in a hard sci-fi setting: there was a pair of characters (man and woman) which traveled through galaxy. The story was told in a chronological order, but because of time travel (for which a binary star system was used), they often met older or younger themselves, multiple times. There was even a diagram (done by author) of their lives and how the story actually was seen from their point of view: with events ordered as they saw them.
I remember there was a talk about seeing the world from one or many perspectives at once--it was even called with some special words, but as I read only a Polish translation, I don't know how it was named in English.
EDIT: the English words used were: Simplex, Duplex, and Multiplex (thanks to Winchell Chung for adding them in a comment). /EDIT
I think the original was in English, and that it was written before 1990... but I'm not sure. It was a single book, it had maybe 100 pages.
One of the first scenes was that boy (main character) lived on a not very interesting planet and wanted to escape from it. He knew an old lady living on that planet. That lady once showed him a girder bridge that was built on that planet--she said it was modeled after a bridge on Earth. She said that as long as he stands in one place, he cannot see that it is a girder bridge, as he sees it only from one perspective. That lady was actually the same woman he will meet later on a ship (as a young girl), but in her last stage of life.
What was that story name?