Hi,
You should go through "Power Supply Cookbook" by Marty Brown, and other books written by Raymon Mack Jnr, Ron Lenk, Abraham Pressman and Keith Billings.
You should start with a useful book from Kolkatta - "Power Electronics Demystified" by Chandra Shekhar Roy. This is very useful book for SMPS starters. Be careful, there are some mistakes regarding information and circuits there, but overall, it is a very useful book as I find.
Hope this helps.
Tahmid.