Some websites provide free access to eBooks. You should use these with caution:
Some of the main sources of free eBooks are listed below.
Google has a large database of electronic books. For modern books, it often only provides specific pages (rather than the whole book), but these digitized pages are often useful for research.
Project Gutenburg is the largest collection of free electronic books online, containing academic and non-academic material. A large number of these are transcriptions of older books, others have been written more recently for distribution online. Project Gutenburg does not guarantee the accuracy of the transcriptions. You will need to carefully consider the scholarly content of books you find on Project Gutenburg before using them in course work.
The HathiTrust Digital Library is a project that is digitizing books owned by research institutions and libraries. Around 30% of the 10 million HathiTrust books are fully available online. These tend to be older books, so might not be suitable if you are researching a contemporary topic.