This is good for a start, but there's plenty more you could have done to this piece. Namely, you definitely need a solid color palette for the bookcase. A third color would have allowed you to create more detail, and 4 colors altogether lets you do even more.
There is also a lack of light source due to there being no determinable palette. With only 1-2 colors for each portion, everything seems very flat.
Personally, if I really wanted a bunch of books to be in a bookcase, it'd have to be much bigger than this to allow for more colors. But I think that's a huge challenge that shouldn't be tackled just yet, as well.
Overall, it's alright but needs more substance. I suggest looking over these tutorials that I've gained something from, because they might help you too:
http://www.pixeljoint.com/forum/forum_posts.asp?TID=5692
http://www.pixeljoint.com/forum/forum_posts.asp?TID=11299
http://www.wayofthepixel.net/index.php?topic=8110.0
Thanks so much! I don’t really have much of a clue with most of the stuff I am drawing. I just kind of jumped into the deep end. I really appreciate your comments and help though! I’ll give those tutorials a go and hopefully get a stronger grasp on pallets, shading and other things I would have probably learnt if I had studied art at all... haha whoops.