dont tell anyone, but some textbooks you can download off the internet (hush hush) but no, textbooks are not NECESSARY but you do use it alot for referral, you dont need it immediately prior to starting but if you start getting lost needing to look at the lectures over and over or want to get a deeper and more complex understanding, an edge over the other students you should buy them, you wont only use the textbooks subject by subject most of the time you'll refer back to them in the later years of your course and even after you start work as an engineer, its best to have your own personal library when you get to that stage.