Hi there Martin
I'm a little curious as to what kind of book you refer to (i.e. is it a work of fiction or a work of criticism? In other words is it an original work by an author, or is it a work by another author which includes quotations from the primary work? Or is it a critical edition of a primary work?) Usually, when intial letters are placed in parentheses (), specifically in relation to the example you give, it means that the critic/editor has amended the source text (e.g. replaced a lower-case "i" with a capital "I", or vice versa. Don't know if this is of any help. I hope so.