1
It’s a very interested book.
It’s a very interesting book.
Use interested to describe how someone feels: ‘I’m interested in this book.’
Use interesting to describe the person or thing that produces this feeling: ‘This book is interesting.’
2
She didn’t seem interested to know the truth.
She didn’t seem interested in knowing the truth.
Use interested in + noun/-ing for an activity or subject that attracts someone: ‘She’s interested in learning Spanish.’
We can use interested to + infinitive, especially with verbs such as know, hear, learn, see and read, when we are curious about or react to information: ‘I’d be interested to know your opinion.’ ‘I was interested to hear the news.’