LDS apologist, Mike Ash, published an article challenging the traditional LDS reading of Alma 39 and the sin next to murder; instead of arguing that Alma's concern with his son Corianton was about sexual transgressions, Ash understands the phrase and concern to be about the destruction of one's faith/testimony with Corianton's denial of the gospel to embrace heresy, a reading I find to be exegetically persuasive. One can find the article here.
Mike has also written two very good books on LDS apologetics:
Mike also wrote a response to the CES Letter, Bamboozled by the “CES Letter"