Hello kissy1097,
If you need to use books as part of your research, it probably makes sense to go to your local library and see what books they have on Inflammatory Bowel Disease. There have been dozens of books written over the years, so depending on the size of your local library, you might be able to access a few different ones.
If you live near a college or university you might also want to see if you can access their library as that is another likely source for books on IBD.