Hi,
There are several books available see this site for details
http://www.certificationbooks.com/ There are also other books that are considered reference manuals like 'Core Servlets and Jsp's' (have a look at amazon for others).
The thing is to find a book that helps you. The Head First series helps a lot of people but there are some who do not like its style. I recommend that you have a look in your local book store at any Head First book by Oreilly. The Head First servlets and Jsp's book takes the same format. If you can learn from that, or tolerate the style then go for it, if not try another book. Most people here recommend it and at least 2 of the three authors have been know to post on this list, which helps, and they helped write the exam, which helps even more.
I would strongly recommend that if you are only going to buy one book, you have a look at other free stuff on the web and ask lots of questions here.
Good luck - you can do it but it may be touch at times particularly if you have never done any web programming, it is a very different paradigm than gui stuff, and it may take you longer than a month - depends how much hard work you are prepared to put in.
HTH
Mat