Here are list of references I am studying
1 - Principles of Geotech Engrg - Braja Das
2 - CERM
And list of Test books I am practicing:
1 - six-minute solutions for PE civil geotech
2 - Civi PE Geotechnical by pe prepared
3 - Geotechnical depth problems by bruce wolle
4 - Practice Tests...
I recently found this one very helpful for exam prep:
Practice Tests Kit for PE Civil Exam - Geotechnical: A practice test book to prepare engineers for PE Civil Exam - Geotechnical Depth by Amazon.com
https://www.amazon.com/dp/197767545X/ref=cm_sw_em_r_mt_dp_U__zU4mCbFXZJX9Q