Without giving it away, I'll quote the hint from another forum user:

As covered elsewhere... consider what the book in the switch room says, then look at the mini-map, and the floors of surrounding rooms. If you interpret what you see correctly, you'll have the clues necessary to solve the puzzle.

This puzzle is definitely the one I've gotten the most complaints about. It's an optional quest, so it never became priority to improve it. I plan to redesign it for the next release of Flare.

In the big room with the 8 switches, the book should be in the center of the room: https://i.imgur.com/KGasOVD.png

Are you playing on Android by any chance? The "version" of Flare on the Play Store is a fork of our game and not done by us. It's using an older copy of the game data, which I don't think has said book. I highly recommend playing the Windows or Linux versions we officially released.

when i push to book i see only http://www.imageup.ru/img103/3014200/flare1.jpg.html

@gruz That is the hint. IT's a bit vague. I've already decided that we'll be redesigning this part of the quest for the next release: https://github.com/clintbellanger/flare-game/issues/711

Just tell me WHAT SHOULD I DO IN THIS FUCKING ROOM? I solved this puzzle for five hours. I have no more ideas for solving it.

Here's the solution (spoilers obviously): https://i.imgur.com/EasfXwr.png

This puzzle has been redesigned for the next release. Here's a screenshot of it in its unsolved state: https://i.imgur.com/5EMfaQV.png. If you were able to solve the previous puzzles in this dungeon, the solution for the new one should be much more obvious.