I think both are used, in different situations. (A little different meanings.)
1.I am interested in reading your novel.
(indicating what you’re interested in, habit, hobby, or something like that)
You may say that in your introduction when the first you go to a course: Hi, I’m Bryan, [color=red]I’m interested in watching girls, so please I want to sit by them.
2.I am interested to read your novel.
(indicating the act you’re going to do)
You may say that before you do the reading: Your friend Luke is a celebrity writer and he just finished his latest novel and he put the book on your hand, then you said ‘Ohh, OK, [color=red]I’m really interested to read right now’.
I am interested to read your novel. - i dont really think you can say that.
I am interested to read/find out/know that you are the champion (It is interesting to read/find out/know that you’re the champion - you are not interested in reading, only in the fact)
I am interested in reading your novel (You’re interested in the process)
Just my 2 cents
This is what I meant as you found out in your textbook: <interested/excited/satisfied + to + RV>:(indicating [color=olive]the act you’re going to do)
I’d be interested [color=red]to know what you think about the idea.
[color=olive]I’m going to know your idea.
I am interested [color=red]to see that the goverment is interested in building more hospitals.
[color=olive]The government is going to build buildings.
[color=green]I’m interested to read/learn (the news) that we have won. (correct)
[color=red]I’m interested in reading that we have won. (wrong)
[color=green]I’m interested to read your novel (right now). (correct) I feel interested to do the reading of your novel right now.
[color=green]I’m interested in reading your novel. (correct) I’m your loyal fan, my hobby is to read your novel, and I’m pleased with it (all the time).
I disagree that I’m interested to read your novel (right now). is correct.
Though, I’m not a judge here (because I’m a non-native English speaker ).
Therefore let our Teachers help us decide if it is correct or not.
I’d say that Alex’s (lost_soul’s) description is pretty good. Perhaps you could also say that ‘to’ can be used after ‘interested’ when you refer to a specific, concrete fact and/or completed, real act:
Compare these sentences:
1. I was interested to learn that he had changed his name.
2. I was interested in learning whether he had changed his name.
1a. I am interested to learn that he has changed his name.
2a. I am interested in learning whether he has changed his name.
In sentences 1 and 1a, the change of name is factual/real and already completed.
In sentences 2 and 2a, we don’t know if the change of name is factual/already done.
I also agree with Alex that this would be a correct sentence:
I’m interested in reading your novel (right now).
I would probably understand that to mean that you want to read the novel but haven’t begun reading it yet.
However, if you have already started reading the novel, I think it would be more typical to say something like this:
I’m reading your novel right now and it’s really interesting.
I would also say that you can use either ‘in’ or ‘to’ in some sentences, but when in doubt, using ‘in’ is probably the safer bet.