Hi everybody,
I am an engineering student who has always been fascinated by psychology .So I downloaded a bunch of books about psychology but it seems there are too many of them and that makes me so confused,I don't know where to start.

Could anyone tell me which books should I read first as a beginner?

Is there an area you want to start with? Do you want to read textbook-type books on psychology? If that's the case, I'd recommend something about the Theories of Personality (or a similar title) and something about Abnormal Psychology. You also might want to page through one of the DSM editions (the official handbook of mental illnesses).

Or do you want to read some of the best self-help books to see what the general population is reading?

Your academic and public libraries should have all sorts of good stuff on their shelves. What have you downloaded?

As you read, make a list of famous names too, from Freud, Jung, Horney, etc, and plan to read some of their books.

I am more interested to read about abnormal psychology.It would be great if someone can recommend me with books which can enlighten me with the basics of abnormal psychology.

Understanding basic psychology is the basis for understanding abnormal psychology.
If you just want to jump in the middle in a non-scholarly way, try
DEVIANT BEHAVIOR
Alex D. Thio, Jim D. Taylor, Martin D. SchwartzISBN-10: 020520516X
ISBN-13: 9780205205165
for a textbook,

and 'Confessions of a Sociopath' for a biography.

For mental illness, start with the DSM manual Wondergirl mentioned.