Rabbi Ori Betzalel Fisher, who is a rabbi in Yeshivat Karem B'Yavne in Israel,
has written these books and is giving them to us in digital form:
"I wanted to say that myself wrote four books regarding laws of gerut.
The second book deals in great detail the meaning of gerut and about the greatness of the gerim.
Whoever wants the volumes, can receive from me.
The third and fourth volume is sold by Yafe Nof Publicatinos. I think it is also sold by Feldheim in America.
They are all in hebrew."