Suggested Reading Pertaining to the Gathering  

"Wherefore the decree hath gone forth from the Father that they shall be gathered in unto one place, upon the face of this land, to prepare their hearts, and be prepared in all things, against the day when tribulation and desolation are sent forth upon the wicked." Doctrine and Covenants 28:2d

Doctrine & Covenants Book of Mormon The Holy Scriptures Church History
Section
3:15c,e
26:3c
28:2c-d
36:12f-g
38:4d-f
39:5c
43:3a,d,f
45:6d; 12a,c-d; 13a-c; 14
57:1a-g
83:1a-c
98:4g-h
108:5d-f;6
127:7a-b
140:5
2 Nephi 7:29

2 Nephi 9:47-49

Matthew 23:27

Genesis 9:21-23
(The gathering is one of these commandments!)

Volume 1, p. 515

Volume 3, p. 653

God's Great Gathering, by Stevens (especially Chapter 5)
My Word, My Glory, by Zerr
Home To Zion, by Winholtz and Holik