Planning to take GWAPT Challenge Exam

in GIAC
So after passing my GCIH, I am planning to take GWAPT as my next SANS Course. I'm not sure if my employer are going to provide my training but for now, I am planning to purchase the exam using my savings. Is it worth a try? Any recommended books that I need to read before taking the GWAPT exam? I am new to Web App Pentesting so I think this is going to be a long study for this year 2017 before I'll book my exam.
Thanks in advance for the comments.
Thanks in advance for the comments.
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