Here's an essay from the Sydney Morning Herald on the subject of "Second-Novel Syndrome."
In short, SNS is an author's feeling of inadequacy when faced with the prospect of writing her second novel--the nagging fear that "I can't do it again."
I haven't felt SNS yet, but that may be because: a)I'm a pretty methodical writer, and b)my first novel hasn't been published yet! If anything, I hope that my second novel will be better than my first, because writing the first taught me so much. I do believe that writing the second novel will feel different. I have a challenge that not all writers face: the second novel is a prequel to the first. That means that I have to go back in time and depict characters who were middle-aged adults in the first novel as young people in the second novel. How they appear in the prequel must be faithful to who they eventually become.
The other challenge of writing a prequel is that the reader already knows how the story turns out. But, as I've noted before in this blog, genre fiction is always predictable. The outcome of the plot is not the compelling aspect of a genre novel. What matters is how the author resolves the plot, and whether the characters are substantial and organic enough to allow the reader to invest in them as real people.