Should a Christian read books known to be heretical / blasphemous / against Christianity?

In short, no, not if you don't have a very good reason to do so. Traditionally, in Catholic seminaries, there was a section of the library called the "Hell Section" and a seminarian had to get permission from the rector of the seminary in order to go into the Hell Section -- which was locked -- to get a book contained therein. The simple reason for this degree of precaution is that one is not allowed to put their Faith in danger with a serious and compelling reason.

The concept of prohibiting books is silly, all knowledge from both sides of the spectrum are viable sources. It is for the reader to discern what makes sense and what doesn't make sense. Would an atheist feel prohibited from reading the bible, just because he/she isn't a proponent? No, of course not, never fear knowledge, only fear the prohibition of it.

I am not suggesting that we are not to guard our hearts and minds. It is important to remember

Romans 12:2 (KJV) which begins;

And be not conformed to this world; but be ye transformed by the renewing of your mind,...

When operating in the world it seems important to not go blindly. When faced with debate about evolution, for example, it would be difficult to debate the issue intelligently without having studied Darwin's theory, and more importantly, read his books and papers. There are some extremely important points Darwin made regarding evolution that most people are unfamiliar with. His own criteria for proving evolution valid has dashed Darwin's theory to pieces.

When faced with this debate with a non-believer, it is amazing to watch God reaching someone by using Darwin's own criteria as a debate point against evolution. This couldn't have been known during his time but, the window of time he gave archeologists to find the millions of shape-shifting fossils he predicted would be found has come and gone by decades. He said that without these, his theory would be without merit.

Romans 12:2 continues;

...thay ye may prove what is that good, and acceptable, and perfect, will of God.

Knowledge about the enemy, coupled with God's wisdom and timing, may just be what God needs from us to be there to help lead an unbeliever to our Lord.

Scene: The captain's office in a frontier fort, somewhere near enemy territory. Enter a sentry.

Captain: What is it?

Sentry: I think it's possible that there may be some enemies out there, sir.

Captain: Enemies? Where are they? How many? How are they armed? What direction are they heading? Are they coming here?

Sentry: I'm not really sure, sir. I didn't like to look at them too closely. I thought it might be demoralizing. So I just kind of kept looking at the wall of the watchtower, where it's safe. But I'm pretty sure there's someone out there. Somewhere.

If you don't read these books, how are you going to know what they say?

Yes.

Each of us, even we atheists, have a core set of principles and beliefs at our heart. These are the primary motivating sources for those things we do throughout the day. Based on the principle that it's better to be motivated by a truth than by a falsehood, I would say it is imperative for all people to continually challenge and refine their internal motivations.

Which is one possible reason why, for example, you might find that atheists in the USA at least tend to know religion better than believers.

I would like to quote the apologetic mandate verse

1 Corinthians 7:1-2 (New International Version)

We demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ.

The new atheist movements books as hard as they are to swallow is good books to have under your belt as a Christian. They seem to be the material that lay skeptics most often go to to defend their skepticism.

Good responses will do you well in your own witnessing.

You must read any of these books the same way you would read the Bible and any other work for that matter: in context.

Any deeper examination of your faith by asking question or reading arguments counter to your beliefs, if read earnestly, and in the spirit of truly wanting more understand should only draw you closer to your faith.

For instance "The God Delusion" is a great book for Christians to read, since it can reveal many of the arguments that Atheist have against Christianity and religion in general. It can certainly challenge you BUT if you make a careful examination for and against its arguments it can give you better understanding of the beliefs you have already, or you might change your mind on certain things. In either event you are more enlightened and better informed.

But again, context is important. If you picked up the Gospel of Judas, thinking it was a canonized text of the New Testament, you may come away with a different meaning than if you understood that it was a Gnostic text written probably in the 2nd century.