HarperCollins AuthorTracker/ EBSCO NoveList
Not sure if this has been mentioned before, but the AuthorTracker is a neat little tool:
Not only does it have plot summaries and info about all of the books/audios/ebooks published by Neil through HarperCollins, it also allows you to sign up for email reminders of new book releases.
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Another neat tool, which can be accessed through many public and school libraries in the States, is the NoveList database. It contains publication information for all the volumes of Sandman (including Endless Nights) as well as the novels that have been published in the US, with reviews from sources such as Publishers Weekly, Library Journal, School Library Journal, and Booklist.