I would suggest, if you have a tool in house, kindly refer the user manuals dude. they help a lot. I have seen hell a lot of ppl refering only the userguides/ manuals. Believe me just grab a user manual of DFT complier or whatever tool you have and start reading them. You will learn faster. Books and all with come later, when you need to design a DFT Architecture. If you are at a learning stage, Then User Manuals are the best to start with.