Исправьте ошибку - I have been interested in space travel ever

 I was interested in space travel ever since I had read a book about it.

We cant use Present perfect and Past Perfect together. The first part of the sentence is Past Indefinite and the second part of the sentence is Past Perfect. (I was interested, since I had read). After I had read about it I was interested in it.

 Past indefinite is used for a past common action. We use the second form of irregular verb. Was is the second form of to be.

Past Perfect is formed with the help of the second form of the auxiliary verb to have had + the third form of verb.