Hi asahin11!
It depends on what kind of antennas you are looking for or if it is antenna theory in general.
There is some books I can recommend, one of them is the well known
THE ARRL ANTENNA BOOK which cover most of the antennas ever made.
And the second is a german book called Karl Rothammel antennenbuch.
There is lots of good books on this subject but this is one among the best if you ask me and if you search the web on antenna theory you will get tons of interesting sites.
For antenna analysis there is a software called MMANA which can be downloaded for free, excellent program.
Can be downloaded here: http://mmhamsoft.ham-radio.ch/mmana/index.htm
Hope this helps.
Bjorn