The Target novelization line was never complete. For quite a few years, the only original series stories that hadn't been novelized were a couple of Eric Saward stories and the ones written by Douglas Adams. Then it finally occurred to someone that getting someone else to write the Adams stories (Gareth Roberts or James Goss) and putting Adams's name on the cover in big letters would probably sell a lot more books than the average Doctor Who novel, and it seems to have worked out that way. We've got Shada, The City of Death, and The Pirate Planet, all released in hardcover, with plans for an unfilmed and unfinished Adams Who story to get similar treatment, even though Adams cannibalized it for his own books already. Unfortunately, Saward isn't quite as big a draw, so Revelation of the Daleks and Resurrection of the Daleks probably won't get official novelizations any time soon.