Signals & Systems 2nd Edition this is an amazing book for all u budding engineers put there-it has everything u require to get ur basics strong so u can tackle the tougher topics later signals and systems is the basics for all electronics and telecm engineers and this book really strenghthens your fundamentals so dont depend on all those tuitions notes and other useless things . it is very well presented and very easy on ur eyes and is one of those books that encourage you to read it dont go for indian books-this ones size might intimidate u in the beginning but is real in a different league compared to indian books like shah and bagali(which happens to have got some of its facts and basics wrong) BUY IT!