is ic reliable as only means to pass clep?

[Matymus]

I think it really depends on the exam. For some exams, yes...IC is certainly enough. For others, no it is not. Western Civ II.........that's a tough one. Simply put, I don't think it's enough for this exam, although...I would recommend Sparknotes.com, Wikipedia.
Here's another link that seems to be pretty credible:

Internet Modern History Sourcebook: Main Page

I hope this helps.