Don't like the way you made your character? Start over. That's the fun part of the game.
Not at all, to be perfectly honest.
Starting a new game is NOT the same as reassigning perks. Not by a long shot.
As for working within the game. Let's start by the magic of it all. The fact that our "perks" are essentially the activation of a star. A star being a hole in the fabric and the light shining through is pure magic. A constellation being a grouping of these holes whose shining magic sums up and governs the strength of the skill associated with it.
I won't say anything regarding time travel as not to spoil it for anyone.
It's simple. You find a cave entrance. This ultimately takes you into a ruin that has all sorts of mobs (spider, undead, skeevers, etc.) and various traps. It also has some puzzles to overcome. By the end of it all you come to a big open room. In the center is a pedestal with a book on it. The room has a dome ceiling to it and etched into the stone going around in a circle are the constellations. Where the perks (stars) are, within the constellation, are glowing gems. The floor of the room is all water but very shallow. Flat calm and reflects the lights shining above.
The book you read and it allows you to basically rebuild your perks one time and one time only. Once done, you are simply left with the book which would have a unique cover and would describe the constellations, what they are, how they work, how they came to be, etc... Making a good book for those who like to collect them for their home shelves.