When reading, sometimes I take in the amount of description and say, “wow, i’m there.” Other times I feel like “where’s the story?”
Description is a difficult part to get right. Some people want to know every single detail, but a lot of us want the story to move forward. The question is, how much is enough and how much is too much? I find myself struggling with that time and again.
Science fiction and fantasy need a different amount of description than some other genres (say, chick lit). When I build a world from scratch, you’re probably going to want to know whether my critter has blue fur or brown scales or even different facial features. That doesn’t mean I need to spend time talking about my fantasy (human) protagonist’s long, dark, wavy hair every few paragraphs.
A lot of times if a detail isn’t used to further my story, I leave it out. I know I need more description in some of the my work, but it isn’t hurt me to get the story out first, then figure out the details that need to be woven inside.
The trick is balance, I think. Then always checking the story after the changes to be sure it still has the plot somewhere and not hidden by all the descriptions. Writers simply can’t describe their world for ten pages and expect the audience to hang out waiting for action. Then again, if we throw them the details in chapter 22 about the critter they’ve been traveling with for the entire book, it’s too late.
Ransom Noble 
I never thought about how much trickier it is for a fantasy writer to write a longer piece. Writing short speculative fiction is one thing but book length adventures is something altogether different. Now I am going to be thankful that all of my book length stories are grounded in reality. Much easier to work that in. It also gives me a new found respect for the science fiction novels that I read.
I have a hard time with description, at least when it comes to setting. I focus more on the characters and what is going on. It’s something that I need to work on and develop a little more as a writer.
Another key is to integrate the description into the flow of the narrative. Instead of spending the first five or ten pages describing the new world as a spectator, have your characters see the world. They can maybe compare it in their heads to things they’re familiar with, and then we “see” it with them. 🙂