PHILIP JENKINS: Dan Brown, Eat Your Heart Out (Real Clear Religion). It's nice to see the Old Testament Pseudepigrapha gettting some wider attention. That said, I remain to be convinced that any of the Slavonic pseudepigrapha listed in the article go back to the Second Temple period. The best case can be made for 2 Enoch (on which see here) although, as the article hints, if there is an early Jewish core, it probably has been developed subsequently in ways we don't understand well. A lot of people seem to think that the Apocalypse of Abraham is early and Jewish, and it may be, but we should be cautious about assuming that its long and convoluted transmission has delivered it to us in pristine condition. But whatever their origin, some of these texts are pretty old, and the suggestion that some of the ideas in them contributed to medieval revivals of Gnosticism is worth exploring.
Philip has more on the subject in his blog post THE SLAVONIC SCRIPTURES. I have lots of posts on Slavonic pseudepigrapha and related matters as well. Start here and work your way back.