As verbose and annoying to read MSDN and Microsoft documentation in general can be, I learned a lot of visual basic and the win32 API as a kid by reading the offline documentation. If it hadn't been so verbose and annoying, I don't think I would have been able to, as once I got accustomed to it, it provided great detail -- enough that beginner-me could piece everything together and write simple games using GDI and other win32 API stuff.

I also learned Python in ~2000 or ~2001 using their offline documentation and the occasional online session (didn't have internet at home at the time, but wasn't completely offline either).