One of the challenges authors face is managing to introduce the reader into the world they are describing without any image to help them. If not taken into account, it could make the reader detach from your story. Here are some tips for drawing your reader into the story.

First thing you need to bear in mind is not to overdo. The objective of descriptions in a book is to make the reader feel they are there, not to draw an exact image with every single detail. If there is too much description, the book could become a rather heavy read. Write the general idea, and leave the rest to your readers' imagination.

One mistake I have seen in many books is focusing solely on what you can see. Your objective is to make the reader feel they are there. Albeit sight the predominant sense, the others evoke stronger sensations. John Barth suggested using two senses along with sight. The smell is considered one of the strongest, so I would encourage to use this when possible.

Another tip is to include small moments of existence to increase the believability of your story. There are some details that, while often go unnoticed, are part of our everyday life, for example, little drawings or marks on the desk or dirty cars with messages written over them. By using them, you are causing the subconscious of your reader to relate with the story they are reading. This piece of advice, however, is a double-edged sword. Since these details are specific, it is hard to introduce them naturally in your story, and by overusing them, you could bore the reader.

The description should be relevant to the story. Take, for example, a situation in which the main character is being chased. For the reader to have a clear image, you should address the chasers (how far they are, their speed, or if they run into something or somebody), the possible ways the main character can confuse them (any alley or narrow street, crowded places). However, it is out of place to describe the Victorian architecture of a building the main character is passing by, however beautiful it is. On the contrary, the architecture of a building could be relevant if a character is recently moving to a new house (accompanied by other subjective details). As well as this, the description can and should be used to subtly introduce details that are going to be crucial for the plot or to give away hints that foreshadow what is going to happen.

You should also bear in mind each character's point of view, especially if you write in first person or third-person limited omniscient. Each individual is different and, therefore, see the world differently. For instance, a dark alley is a source of fear for a woman walking alone at night, but a fugitive will see freedom in it. Some people pay attention to every detail and others hardly notice the person they are talking to. And those differences should be noticeable in the descriptions. 

These differences in the description could also vary with their current mood. Depending on how they feel they'll focus on different aspects. If they are insecure about something, they'll pay attention to everyone around them and the physical symptoms they are experiencing but will put everything else aside. 

To sum it up, the description should be long enough to evoke sensations and be relevant to the story without boring the reader. It should be versatile, changing with the necessities of the scene. Everything that surrounds us has multiple layers to explore, and part of the writing magic is mirroring it into words.