> The project was met with significant legal challenges from authors and publishers which was eventually overcome
I don't think they were overcome. As far as I remember Google couldn't make the books available so they abandoned the project. They possess the scans (if they didn't delete them) but they won't be made public.
The consensus among copyright lawyers is Google lost Authors Guild v Google, but for some reason the media and Wikipedia do not clearly report it that way.
IIRC the courts ruled that because it would be implausibe for a person to use google books previews to read an entire work (you'd have to make a whole bunch of separate accounts to do so), it could not plausibly impact the market for that work.