This book is set in the same Universe as the Vorkosigan adventures, but about 200 years earlier.
It is a much more "straight" work of science fiction than some of the Miles Vorkosigan stories, e.g. it is not quite as side-splittingly funny. The tone and style are quite similar to the two books about the romance between Mile's parents, "Shards of Honour" and "Barrayar."
"Falling Free" is the story of the quaddies, a group of modified humans who have been bioengineered for zero gravity, the main change being that they have four arms instead of two arms and two legs. An engineer, Leo Graf, is concerned at the way the quaddies are exploited and decides to do something about it.
It is a well-told story and highly entertaining.
There are two subsequent stories with quaddie characters set in Lord Miles Vorkosigan's time, some 230 years later. The first is the novella "Labyrinth" which is part of the book "Borders of Infinity" - Miles and Bel Thorne meet a beautiful quaddie musician, Nicol, on Jackson's Whole. ("The Mountains of Mourning" is the previous novella in the same book.)
A better picture of the society which quaddies make for themselves in the future is given in the tenth and currently most recent Vorkosigan adventure, "Diplomatic Immunity" which is set on a space station in Quaddie space.
Bottom line - this is an extremely good book, and if you liked any of Bujold's other SF novels you are very likely to enjoy this one.