There are no quick and easy answers to this question for me, in part because I don't think a first novel is a relevant starting point for the discussion. What matters, in my mind, is the reader's first experience with an author, which may occur with that author's first novel, or may occur at any other point in the author's career. From my own experience, once I've read a bad book by an author, it casts the rest of their work in a different light. If I happened to have started with better work, then I can probably forgive that author for a crummier novel, regardless of when it arrives
in their career. But if I started with a crappy novel, it becomes very difficult to convince me to try something else, perhaps because my experience has already been tainted by a negative. There is always the chance that I'll try something else by that author, but perhaps only with a lot of prodding. After all, there are so many good books already out there -- waiting to be read.
For proper first novels, the process is largely the same for me. If your first novel is crap, then it's not likely I'll return to your work. But so far in this post, I've taken as a given that the negative experience is the result of a truly awful novel. Can I forgive minor mistakes if the overall product is good? I don't know. Maybe? That might depend on the author. Myke Cole's first novel, Shadow Ops: Control Point, is far from a perfect novel, but you'll be hard pressed to convince me to ignore anything else he writes (unless he turns into some kind of foam-at-the-mouth crazy person who thinks we should cut off the left foot of every first born son or whatever).* How much do I care about the flaws in his work? Where is the line between "reasonable flaw" and "complete disaster"? I'm not sure I can define the line at this moment; I'm still stewing over the idea.
In other words: it really depends on the situation. Are first novels forgivable? Maybe. But that probably depends on the answer to this question: What makes the novel needing of forgiveness? If the writing is atrocious, then forgiveness may not be forthcoming. Minor plot holes? Who knows...
What do you all think about this?
*Control Point is a pretty good book. Lots of action. A nice take on superhero abilities, and so on. Plus, Myke is a wonderful human being, as I discovered when Jen and I interviewed him here and brought him on for a discussion episode here.
Note: I'm using "forgive" rather liberally here for lack of a better word. There are very few instances when a bad book causes offense. So take my use of the word lightly.