I really enjoyed "Spock Must Die!" and I loved Blish's reference to the transporter using DIRAC technology (from his short story of the same name)
The only one of Blish's adaptations I've read was "The Doomsday Machine" because he changed the ending somewhat. But I've read all his prefaces, where he answers letters from first-generation fans.
As for Blish's non-Trek works, hunt down his "Cities in Flight" books. Well worth a read.