GMAT specific book for Medium to Hard Questions

Hey,

I am aiming for about a 168 in Quant. I am getting about 165 or so almost every time.
I am looking for some Medium-Hard level questions. Greg always talks about the GMAT material.
Can anyone help me with any specific GMAT book where they preferably have the questions’ difficulty mentioned with them.
Any additional information about the book you could tell me or that would be helpful for me (such as anything to avoid or pay more attention to in the book) would be appreciated.

PS. Would be really helpful if you can also guide me to the soft copy pdf to any of the above materials :)
Thanks.

This goes against forums policy so please avoid taking about piracy materials.

You can buy the OG GMAT book or You can get the quantitative one(This only contain quants and I link it below)

https://www.amazon.com/GMAT-Official-Guide-Quantitative-Review/dp/1119793785