I suppose it depends upon the type of book that you’re writing!
Traditionally, authors usually did a lot of description along with massive preambles, which most readers today would find quite cumbersome. These days, most people simply don’t have the time or the concentration for too much description and prefer to be thrown straight into the action!
So far, the description in my books has been very minimal, as I am acutely aware that the patience of most modern readers hangs by a thread. Of course, if you hook your readers with the story and characters then they’re more likely to stick around, but nobody wants to be bogged down by too much description! As long as you paint a clear picture for your readers, then you have done your duty as a writer.
The description should enrich and supplement the story, not distract from it! If I ever feel that the description is going off on a tangent then I reign it back in, unless it’s important to the narrative. However, some genres naturally lend themselves to more description, such as science fiction and fantasy. In these cases, the readers usually crave as much detail as possible about the world that you’ve created.
But regardless of where your story is set, try to keep the story flowing at all times and prevent your description from stalling things. Rather than have a solid paragraph describing something, try feeding the information to the reader in dribs and drabs. Not only will they appreciate you for it, but they’ll probably remember the information much better too!