To read books, you don’t need to have a tablet or e-reader. You can read books online, in your internet browser of mobile or computer. Most popular sites are listed below.
1) Google Books : https://books.google.co.in/
Google books is a service from the Google inc, which searches the particular search term in full text of the books scanned by the google. Here you can preview the book pages. One limitation is that not whole book is available for reading but some chapters are intentionally not shown. But if you are looking for a particular topic you will almost get the Topic from different alternate books. Google play store has the applications for this called "Google play books" where you can search the Engineering books as well save the preview or sample copy of the book for your offline reading. Almost all major engineering books are available there. You can also save the book pages given in preview to your computer in PDF format using a program. Visit http://www.prophethacker.com/2015/11/download-google-books-pdf-free.html
2) Internet Archieve : https://archive.org/details/texts
The Internet Archive offers over 15,000,000 freely downloadable books and texts. There is also a collection of 550,000 modern eBooks that may be borrowed by anyone with a free archive.org account. There are very old books available also. You can download all books for free
3) Scribd : https://www.scribd.com/books
Scribd is the collection of the various books and is in very large numbers. Almost you will find every book you need in pdf format. Slideshows are also available. You need to regitser you account to use the scribd. There are new engineering books as well as notes also available on scribd.