I see the point for publishers.
As the thread topic was C++, how about “Learning C++ for IOS Development with Unreal Engine 4”? UE4 may evolve at lot, but the basics of C++ don’t, so a good part of the book would be static. IOS development books are obviously still en vouge.
UE4 is $19 (one month is fine if you don’t need updates, there is also already a way to enter a code when purchasing, probably a way to make a deal for a free month with a book - consumers love “get … for free!” stickers on books ;)), Unity for IOS is like $150 a month (if I remember correctly?).
Last time I checked, there were >11,000 subscribers to the UE4 source code, which is probably just a part of the current developer base. My guess would be, that a good beginners book could lead to a huge spike in numbers. For the benefit of both, the book and UE4.
Sounds like a winning formula to me.