it is exactly what I am working on

There are two files in the gui folder, so you can just find them and change them to see. their names are respectively menu_story.png and menu_story_focus.png
Closed book:

ingame:
Now it's done, I give the XCF file I used to do this. In it you can find the old trys and the current book, a grayscale and a coloured background, so it's easy to tick the things you want to see and make any combination you want.
@ hiker: About performance impact, I'm surprised, while my APU makes fine the job for changing smoothly the images in the grand prix selector. But, anyway, it's not exactly for today

Maybe tomorrow

. Do you use nvidia material? (I remember small performance issues on my big playing station, now you say it, and it had nvidia-based GPU. But... the playing station died some days ago (I mean: no beep, no stating, no video output... but it had an old gamer material (Asus commando, Core2Duo,...)
Edit: A big issue tu put in the first priority (or not)

: Now on starting the focus should be on single player mode and not on story mode to see the book opening. Other way to go: don't focus anything at all at the starting if the mouse is not on a button.
Or focus on a "virtual" button out of the screen that you could not see and select with arrows.