Book value per share can grow even with negative ROE, if equity is freshly issued at market price that is much higher than book value - even as earnings are negative. Consequently book value will be seen to be growing, even with losses!!! And growth in book value is then touted as (or mis-led as) economic performance of the firm.
I had some time ago shared an example of Fairfax here - Quess Corp - Human Resources Company - #9 by diffsoft
In any case, to be clear, my post is not a comment on the value IDFC First. It is to show a certain kind of caution to be exercised.