I don't think there's a magic bullet here. I used to fly heavily for work (not 25 hours, though) and would get by on a combination of:
* Podcasts (I highly recommend
$1,
$1,
$1,
$1). They're free, interesting, and plentiful.
* Audio books. I know you've mentioned this was your go to, but I have listened to What the Dog Saw & Outliers, both of which I'd highly recommend.
* Regular e-books on the Kindle, iPad, etc. Not sure if your friend has the ability to read, but hey, they're always an option if he/she can.
* Have a glass of wine after your big meal and pass out. If you're in business class and can sleep, SLEEP! :)