Dear student,

There are a lot of websites available on the internet, from where you can download the engineering books. There is no such a fix website, as there are too many websites. Just type the Book and author name on google and you will find pdf's related to it. Hence download it from there.

Also, some websites will cost you money for downloading these books. And also some are totally free. So, check them as per your choice.

Hope this helps.