From the Guardian:
An unfinished tale abandoned by JRR Tolkien in 1918 has been completed by his son and will be published next spring, it was announced yesterday.
Christopher Tolkien has worked for 30 years on an edited version of The Children of Hurin, a story set in the legendary land of elves, hobbits and dwarves depicted by his father in the epic trilogy The Lord Of The Rings.
I realize that every situation is different, and obviously, I haven't read his completed version. But. For the most part, in these situations, I vote Don't Do This. Example? The Bellairs stories finished by Brad Strickland. Pbbbbbtht.