I spent the better part of six months researching biblical end-times scenarios, possible ways that the world could fall apart geopolitically, super-viruses, and another six months outlining my novel to incorporate all of that knowledge. One of the biggest problems that period novels have is when the research takes over the novel entirely.
For example, a novel is set in London in 1798 and the writer has done extensive research. The storyline is very well plotted, with characterization that causes us to see these characters and how they must have lived in their era, but then the author spends the next fifteen pages explaining the history and culture of the time period, leaving us wondering what happened to those wonderful characters.
In my current novel I had to find the balance between telling my readers about the fictional future timeline I had carefully constructed and simply letting my characters live in it and allow the reader to experience it through the eyes of those characters. I am finding that leaning more toward the latter view is what is causing my novel to be more engaging rather than boring people with the bitter details of our world's demise.
Once in a while, in the dialogue or in an inner monologue, I will spend maybe a short paragraph filling the reader in on the events of the future-past, but it is always very brief, poignant and meshes well with the action of the plot. It is important to remember that we novelists are storytellers, after all, and we must entertain our readers enough while showing them how artful we can be with our words and possibly sailing our heart's message across the sea of their indifference.
If we bog down our novel with long historical cataloguing, we ruin the point of why people pick up fiction novels, and that is to be engaged, to escape, and to hopefully think about the human condition.