Undergraduate doing a research term - supervisor has not assigned me any work to do other than reading, after one month. What can I do to fix this?
As an undergraduate, it is not normal for you to be expected to come up with the research project on your own (that is what getting a PhD teaches you!). When I started out I was typically assigned a graduate student advisor who would let me work on their project or would work directly with me to propose another. 

There is typically a lot of reading that you will do when first starting out, but not applying it directly to a project or research proposal after a month indicates that something needs to change.

I would first talk about these matters with someone who understands your supervisor (graduate student, postdocs etc.) to understand more about your supervisor's expectations. Then have a talk with your supervisor with your concerns (they are valid!). If your supervisor continues to not be helpful I would consider finding another. It's tough to start over, but it would be better in the long run if you can find a better lab that is more nurturing to your growth as a researcher.