Learning in depth I think is an aspect of the path of the Gra. The most important of the books on learning in depth are all from the path of the Gra. Not just after Rav Haim from Brisk but even before him. Might as well make a list. The Hidushei HaRambam of Rav Haim of Brisk. Shimon Shkopf the Shaari Yosher. R Akiva Eigger. Netivot HaMishpat. Baruch Ber of the Birkat Shmuel. Ketzot HaChoshen. The Musar movement. Naftali Troup. Aruch Hashulchan. The two commentaries on the Yerushalmi, Pnei Moshe and Karban Eda both direct disciples of the Gra The peak is of course the Avi Ezri of Rav Shach. But besides that there are countless of deep and great books by the great people of the Lithuanian Yeshivas which are all of amazing depth.
But I have to add that the path of the Gra to a large degree meant trust in God. People were not worried about making a living. Trust and learning Torah in depth are the two pillars of the path of the Gra.
[My thought is to at minimum get the Avi Ezri of Rav Shach and do each section many times until it becomes clear.]
rav nachman of breslov whose conversations were complied in a book called. In chapter 76 Rav nachman introdues his idea of learning fast (bekiut). That is, "To say the words in order, and go on." However in the book of his Torah lessons the Le.M. Vol I chapter 78, he brings the importance of in depth learning. From this I found ways to learn-both math, physics and gemara rashi tosphot, maharsha.
