The most recent scholarly materials that I know of are primarily Volodymyr Serhiychuk's books from Kyiv. I recently got a copy of "Поляки на Волині у роки другої світової війни" published by the Kyiv state University in 2003. He has another interesting book - about the Deportation of Poles from Ukraine which was published in 1999 which I used for an article not long ago about Polish deportations. I'm gradually working my way through the book. Another interesting book is Mykola Siwicki's book Записки сірого Волиняка published in Lviv in 1996 which is also very interesting