How do we change Wh questions into indirect speech? Is it similar to Active & Passive voice?

When the interrogative sentence is not a WH question, we use if and whether. And, when we have WH questions, the reported speech remains the same as the question itself except the fact that the tense changes. 

For instance, 

• She asked me, 'Which book are you reading'?

  This sentence changes to:

  She asked me which book I was reading.