You may study any book such as MATLAB for beginner, or MATLAB for engineer. Try search at the EDAboard Ebook Download/Upload. MATLAB Help is a great source to learn about it.
I suggest a mix of the two:learn basics (defining vectors,matrix,transfer function,plots...) from a book and then do a massive use of the excellent online help. Remember that you can always write "help ****" in the command window to know all about **** function (it's really useful")
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The best book to start learning matlab is the one by rudrapratap singh...if u r in a college should be available in ur coll library....once u r done wid it u can turn to various toolboxes according to your need...in that context matlab help is very good