BUT WHAT IS IT?
In a nutshell, Fridge Logic is considered any logical inconsistency or plot hole that you missed while you were reading (because you were so wrapped up in the story, you just didn't notice it, or whatever) but that comes to you much later when you're really thinking about it. It's basically all that picking-apart of plot elements that people do long after they've read the book. It's a "wait a minute..." moment.
An example: you have a character who has to get from Los Angeles to San Francisco in a very tight timeframe. Say, three hours. So they hop in a car in L.A. and somehow manage to make it to San Francisco with time to spare. Now, anyone who lives in California will probably realize that this is LITERALLY IMPOSSIBLE, even when one is driving 100 MPH the entire way. But people who aren't familiar with the geography of the state and/or who just aren't paying close attention to the timeframe might not realize the logical inconsistency here until much later when they look up how far apart L.A. and San Francisco are and go "... wait."
Is there anything you can do about Fridge Logic? It depends. I think it's sometimes easier to minimize Fridge Logic in novels than in television, since television operates under pretty strict time constraints and has to worry about keeping audience attention with the flow of the script and all that. Television writers can't risk losing an audience's attention by listing out the painstaking logic of every little thing. And really, neither can novelists. That would make for a very boring book.
However, you do have more room to stretch and really solidify your world-building in novel form. I don't know that I've ever come across a novel that couldn't be picked to pieces on some level, but some are certainly better than others at consistent logic and closing plot holes as best they can.
In the end, it's up to the author to figure out the logic of their own fictional world and make sure it's not completely flimsy. It's up to us to decide what's truly important for the story we're trying to tell and maintaining the audience's suspense of disbelief, and what we can gloss over a little. It also usually helps to avoid breaking the rules we've set up for our own world.
But most of all, try not to sweat it too much. Someone somewhere is always going to be able to pick apart your plot and point out logical inconsistencies. No one's perfect. That said, it's no excuse to get lazy about building the strongest and most hole-free story you can.