[quote=joham;239240]Michael Swan says in his PRACTICAL ENGLISH USAGE that we use 'be interested in doing sth' when we want very much to do something that we haven't done before. But did he say you could not use it in other situations?
But in one of China's senior middle school textbooks there are two sentences with 'interested in doing' that don't match Swan's advice:
1. He is greatly interested in observing the movements of stars.
2. Stephen Hawking has always been very interested in learning about everything around him.
The actions in both sentences seem to be in progress, rather than something that they haven't done and want very much to do in future.
If someone is collecting stamps and enjoys stamp-collecting very much, can we say 'He is very interested in collecting stamps'? Yes, you can.