By so far I have been learning from Theory of structure by Ramarutham, it has been really easy to understand the concept very easily with this has a lot of examples to practice with, this Book can also help you with the competitive examinations for Govt. joba and interviews too.
Another I would also recommend is From B. C Punmia, which has been really help specially with"Influence Line Diagram" which is really a thing for starters to get.