Complex sentence: It has, however, been the subject of many critical surmises and discussions in the course of the last century, and recent discussions have thrown considerable light upon the problems connected with this Gospel, with a large literature around it.
Split into simpler sentences: It has, however, been the subject of many critical surmises and discussions in the course of the last century. Recent discussions have thrown considerable light upon the problems connected with this Gospel, and a large literature has grown up around it.