It could mean that there is no single, solitary novel. Maybe it implies that there are related works or a series rather than just one stand - alone novel.
Well, 'no solo novel' might suggest that a particular work is not an individual entity in the literary world. It could be part of a collection, or perhaps it is so interconnected with other works that it cannot be considered alone. For example, some novels are part of a trilogy or a larger saga, and in that context, they are not solo novels. They rely on the other parts of the whole for a complete understanding.