Books (printed or electronic) are perfect for learning the general theory of a new topic. They should be your first port-of-call when starting your research.
An ebook is an electronic version of a printed book. You can read it on devices such as a computer or tablet. Ebooks are available online 24/7.
Google Books gives access to millions of scanned books, usually only their fragments, not full text. It searches inside books; therefore, it is good for researching topics normally covered on only few pages in large volumes. Some books are better and more appropriate for academic study than others, therefore always check:
Who are the authors: are they researchers or university tutors or experienced professionals/practitioners? Does the book have endorsements from other researchers and university tutors?
For whom it is written: various books are written for different audiences, e.g. general public, undergraduate or postgraduate students, specialists in a particular subject. Choose those that you can understand and leave aside those that don’t make sense or seem too basic.
Who is the publisher: have they published other academic titles? If the publisher is obscure or unknown to you, check again that the author is a reputable researcher and that the book has endorsements from other researchers and academic institutions.