Below is a small sample of open access non-textbook books in nursing. Others may be found by searching Directory of Open Access Books or Oapen.
Aging well: Solutions to the most pressing global challenges of aging by 
COPD Primer by 
A Life Course Perspective on Health Trajectories and Transitions by 
Nursing with a Message by These links open to listings of books dealing with nursing, health or medicine. For help searching more specifically in these sites, please contact me or Ask a Librarian.
These are ebooks that are available to your students for free through USM LIbraries' licensed content. They are not open source publications, and have standard copyrights, but they are available for use as texts. These are some examples; additional titles are available via Springer Link and Proquest Ebook Central.
Understanding Pharmacology in Nursing Practice by 
