One of the Internet’s great sites is Steve Trussel’s: http://www.trussel.com/
This can keep you involved all day, so you might want to go directly to the book section at first, at: http://www.trussel.com/f_books.htm
There is something for everyone here, and just reading through from start to finish provides a course in Knowing Books 101. If you have a question about anything that has to do with books, you’ll likely find an answer here, or a link to the place where you’ll find it.
One of the most useful sections is SetMaker where odd volumes can be listed for sale or wanted, in an effort to reunite sets of books. There is an explanation of ISBNs and how they work, a currency converter, metric and Roman numeral converters.
There are links and subscription information for the major book lists and search engines, to major library catalogues, to shows and seminars. There is information on book terms, dust jackets, bindings, Modern Library, the Encyclopedia Britannica, pseudonyms. And then there are Howard Fast, Lafcadio Hearn, Maigret, and Sherlock Holmes on postage stamps.
Jill Morgan of Purple House Press has amassed samples of 634 author and illustrator signatures (as of September 2002) so you can be sure that what you have is the real thing. http://www.purplehousepress.com/sig.htm
Looking for a book that everyone knows about, but no one has ever seen? Visit The Invisible Library–a catalogue of books that appear in other books, books that never were. http://www.invisiblelibrary.com/index.html
What does it mean? An authoritative site that explains book terms from Stanford University explains it all. http://palimpsest.stanford.edu/don/dt/dt0226.html
If Nancy Drew books are a mystery to you, try this. http://www.stratemeyer.net/stratemeyer/drew/drewform.htm
Greek to you? Or Latin? This is an outstanding site for information on the classics in English, Greek, and Latin. http://www.artsci.wustl.edu/~cwconrad/classics.html
This site is helpful for kids’ book research. There is some pricing guidance, info on illustrators and authors, and a special Wizard who will help to identify books like, “It had a cow in it, and was red. All I remember is that the cow went to Starbucks and got a latte.” http://www.thebestkidsbooksite.com/