I want to know, are e-books (digital version) comparable to physical books in citations? Can I use only e-books instead of real books for finding citations, notes to put in my Bachelor thesis?
Yes, you can. There is absolutely no difference in the citing a digital material of the same printed book as a reference. You may cite the e-book just the way you would do with the printed book. This applies not only to your bachelor thesis but to all publishable content. Just make sure you get the edition and the page references, pp, right (if any).