Is there a list of books that Project Gutenberg wants?
No. Project Gutenberg, as such, does not “want” any specific books. Individual volunteers choose what books to produce. Nobody gives orders to volunteers about what they should work on. Nobody has an official “hit-list” of books to add to the archives. Of course, individual volunteers and non-volunteers have their preferences, and may suggest books to transcribe, and such suggested lists pop up every so often, and are often useful to people looking for ideas. There are usually some suggestions in David Price’s InProgress list. The On-Line Books Page has a section where people can list requests, and Steve Harris has a site devoted to lists of books not yet in Gutenberg or elsewhere. Treat all of these lists with some caution, since someone may have started or even finished one of their suggestions since they were last updated.