An affix comes after a word in the Accusative -2nd case in construction in the sense of 'made in relation to any subject' when the thing made is a 'book'.,
The word अधिकृत्य means 'aiming at' 'alluding to, referring to'. Thus सुभद्रामधिकृत्य कृतोग्रन्थः = सौभद्रः 'Saubhadra or a book relating to the history of Subhadra.' So also गौरिमित्रः, यायातः, किरातार्जुनीयम् ॥
Why do we say ग्रन्थे 'when meaning a book'? Observe, सुभद्रामधिकृत्यकृतः प्रासादः 'a palace built in memory of Subhadra'; where there is no affix.
Vart:- The affix is elided diversely when the book is a story. Thus वासवदत्तामधि कृत्य कृता ऽऽख्यायिका = वासवदत्ता \Vasavadatta, a story relating to Vasavadatta.\ सुमनोत्तरा, उर्वशी ॥ Sometimes the elision does not take place, as भैमरथी ॥,