A perennial question at the library is, "What is the correct order of the Narnia books?" I should know this; these books are classics. But I usually have to go off looking for the answer. Solution: a wonderful C. S Lewis site, offering booklists, synopses, biographical notes, news, and much more.
The order of things is important, and the order of books is a huge issue for dedicated readers. I have to admit that I'm working my way through Ian Rankin's books this summer and have frequently visited this site.
Many Nora Roberts fans have been set off in the right direction here. Patricia Cornwell readers should check this out. This site kept me one step ahead of a patron who's a voracious reader of Christian fiction. Janet Evanovich readers may want to consult this, but for the most part they just need to be able to count.