want to start planing ahead if you have someone going away for school or staying at home for school. Even though more and more resources are electronic these days books and "stuff" still need a place to hang out. Since shelves can be fabricated to be built in or portable you need to figure out how to handle the load they will carry. This URL is a good candidate as a bookmark for almost any woodworker, It has been around and used for years but I'm posting it again as a reminder or a catch up. The numbers you put into the form would work for storing canned goods or tools around the house or shop.
http://www.woodbin.com/calcs/sagulator/Note, the specie block has a lot of lumber listed but you need to go completely through the listings until the end to find ply MDF etc. if that is going to be your construction choice.
ALSO: Read the notes below the form they will help in your input. At the very bottom of the page are some references which might be useful for those who have a more engineering type background or a bigger project in mind.