There are many shops in Amritsar - here is one
Singh Brothers
Bazar Mai Sewan, Amritsar-143 006
S.C.O. 98,City Center, Amritsar-143 001
Tel:183- 550739,545787
Here are some that i read -
1. Sant-Baba-Attar-Singh-Ji-Mastuane-Wale (Very inspirational short book) - online link - Sant Attar Singh
2. Se Kinehiya - (Inspirational short chapters) - online link - already posted by Mehtab (http://www.sikhroots.com/index.php?option=com_docman&task=cat_view&gid=73&Itemid=76)
3. "Pachmi Parkash" - Sant Karam Singh Ji Hotimardana Wale (Very inspirational) - same as above online page
4. Jail Chittain - Auto Biography of Bhai Randhir Singh - Another very inspirational book - Especially the chapters preceding and following "Akaalee jot di darshan"
5. BASANT BIHAAR - (Very inspirational book on the life of Sant Baba Basant Singh ) - http://www.gurdwara.org.uk/gurdwara/media/literature.html
I havent read Biography of Bhai Rama Ji - but i hear its very good as well
If you want to listen to audiobooks of Bhai Randhir Singh ji - You can listen here - http://akj.org/skins/one/list.php?ba=1&b=6&p=misc