If you want to be a generalist, you may want to learn things which are useful independently of the programming language.
Some books that would qualify in my opinion (as examples):
- Code Complete: A Practical Handbook of Software Construction, Second Edition by Steve McConnell
- Facts and Fallacies of Software Engineering by Robert L. Glass
Learning the different approches taken by multiple programming languages is certainly useful. It may not be that much relevant which language it is unless you want a job specifically in that language.
I can't speak for Google but I guess it is more relevant how familiar you are with software development practices and general knowledge about architecture, design, testing, algorithms to name a few than a specific language.