This is why I have confined myself to novels concerned with the period before 1914.
It is for this reason that I have confined myself to novels concerned with the period before 1914.
It = that I have confined myself to novels ~ ?
or
The reason why I have confined my self to novels concerned with the period before 1914 is it (for example, much money) ?
How can I understand this sentence correctly?
This is why I have confined myself to novels concerned with the period before 1914.