It's important to write rich and descriptive text, a fact I've expounded upon more than once, but you also have to learn how to edit out all the uninteresting details, too. In any book, there are several plot points you need to hit to make your story work. All of those scenes should be vivid and embellished, so the readers can see all the events unfolding in their mind's eye. But there are always additional moments that happen in-between the action...and I really don't want to know a whole lot about them. If you're going to write books, you'd better learn how to summarize the boring moments and skip ahead in the narrative.
Details, Details, Details
Lots of readers love long books, and I used to. Half of the enjoyment of the later Harry Potter books lies in the fact that they're massive. But no one wants to read a whole bunch of nothing. Some details aren't important.
Your characters live a life on the page...but let's face it, every moment of that life can't possibly be interesting. Maybe your character spends a Sunday just hanging around the house in sweatpants eating peanut butter and jelly sandwiches. What I really don't need is a long, descriptive post about the making of the aforementioned sandwiches. I know what it's like to sit around and do nothing, and most people are sure to be fairly familiar with the mechanics of a good old PB and J. Every hour isn't enticing, and every day isn't exciting. So you're going to have to learn how to skip them -- and still let me know that they happened, because you don't want a bunch of lost time in your book.
It's not easy to summarize non-events, to skip ahead in a character's life to get to the more interesting parts. But if you don't, and you end up writing hugely detailed passages in which almost nothing whatsoever happens, people are going to skip your books.
Summarizing the Gaps
You can't have a bunch of time gaps in your book (Tuesday we went to the mall and... The next Friday we were at the movies when...), but you also can't have a bunch of useless scenes of daily life where nothing much goes on. Every scene should be relevant to the plot of the story, or offer up some needed information. If it doesn't, it's useless. Sometimes, you've got to skip over the spaces in-between.
The secret to doing so lies in summarizing. It's easy to skip past a night of sleep. You put the character to bed, and the next scene begins with something like "When I woke up..." Skipping quickly through entire days, weeks or months when there's not a lot going on is a bit trickier -- but it can be done with a single sentence. I saw it done once with an entire year. To paraphrase, it went something like Another year passed, in the same manner as the first. This is always an option. Monday and Tuesday dragged by uneventfully. There are a million ways to write it.
But it's not always so easy. You might still need to provide the reader with some information. Something might happen that's not all that interesting, but you've still got to let people know about it. I saw Sheila again on Friday, but once again she walked past me without saying a word. By the time Monday came back around... Again, the secret is in the summary.
Writers tend to be long-winded. That's because five minutes might take 10 pages to pass in a book. So for many, summarizing doesn't come easy. Here's how to make it happen: think about the main points you need to convey; think about how much time needs to pass; write just that information. These bridges between gaps don't have to be flowery, they just need to be simple and succinct. Every sentence doesn't need to be fancy, just like every detail doesn't need to be shared.