There are several factors that go into picking out a book to read. Some people find the lives of others interesting and go out of their way to pick up biographies of celebrities or athletes. Others need a few hours to waste on a rainy day and pick up a steamy romance novel to make them forget about the day they're wasting indoors. Some readers will only read books that are written by their favorite authors or graphic artists such as Drew Magary or Craig Thompson.
Some people don't care who wrote the book or whether or not it's ranked anywhere on the list of the New York Times Bestseller list but only care about the plot. They'll read the book jacket synopsis and if it sounds intriguing they'll read it. It doesn't matter if the book is a fictional novel about an stable hand branching out on their own or a mad scientist looking to create the perfect double rainbow. As long as the book has a great plot it's considered a must read.
Any great book that you can't put down while reading is usually one that has a plot that pulls you in from the first few pages and makes it difficult to put down until you've finished it. You can usually tell within the first ten pages if a book is going to keep your interest or not. Some might start off a little slow and then pick up near the end but for the most part if you're not drawn in within the first few pages then the book probably won't hold your attention for the rest of its entirety.
What is a plot or what is the plot of the book you're reading is a standard question you're probably asked all the time by friends, co-workers or classmates on the book you're reading. You wouldn't answer them with a standard definition of the term plot as that's not what they're after with the question. They know what a plot is. What they're after is the specific plot of the book you're reading.
One of the reasons they will ask you this question is because they are interested in knowing if you read the book. There can be as many opinions about the enjoyment of the book as there are pages in the book. We all have different views on what constitutes a good book. Just because you found a book about the proper use of a pressure gauge or the importance of a home inspection (see here) extremely intriguing, doesn't mean that everyone will find it to be to their taste. That is why people will ask you about the plot. They will wonder if this is a book they might want to read themselves.