SPOILER:
Sent in by Kathy I who says... "This book is very hard to summarize because it consists of three plots woven together, so that you find things out gradually by reading letters (which sometimes describe other people reading letters) describing events which happened years before. It is also six hundred plus pages long. I'll give it a shot, though, by telling the story in chronological order; just keep in mind it loses some of its suspense that way."
Plot one: 1930. Benjamin Rossi, a graduate student in history, finds a mysterious book containing only an engraved picture of a menacing dragon. Through diligent research at Oxford and Istanbul, he discovers that Dracula (or rather, the historical figure, Vlad the Impaler, on whom Dracula is partially based) is alive, hiding in a secret tomb somewhere in Europe. However, as Rossi pursues this information, people close to him begin to die of violence and blood loss. He ultimately decides it is too dangerous to push any further, and goes back to his usual life at school.
Plot two: mid 1950's. Paul, another graduate student in history, finds a mysterious book containing only an engraved picture of a menacing dragon. He takes it to his mentor, Benjamin Rossi, who shows Paul his book and recounts some of the events in plot one. Then Rossi disappears, leaving only evidence of a violent and bloody fight. Paul becomes convinced that Rossi has been kidnapped by Dracula and taken back to his hidden tomb for some unknown evil purpose.
He joins forces with Helen, another student who turns out to be Rossi's illegitimate daughter from a trip Rossi took to Romania in 1930 to search for Dracula's tomb. (Rossi was given a potion to force him to forget this part of the trip, and thus abandoned Helen and her mother.) Paul and Helen, pursued by an "evil librarian" vampire, search museums, monasteries and libraries in Istanbul and Cold War Eastern Europe for clues to the location to the tomb in a frantic attempt to rescue Rossi. They finally find the tomb in Hungary, but too late: Dracula has fled and Rossi has received the three bites which doom him to become one of the Undead compelled to serve the master vampire. (Dracula kidnapped Rossi because of Rossi's intelligence and persistence, intending to force Rossi to become...the curator of Dracula's extensive library.)
With terrible grief, Paul and Helen drive a stake through his heart to spare him that awful fate. In the course of plot two we learn: a) Dracula is the one leaving the mysterious books to students, in order to find brave and brilliant scholars; b) Helen is a direct descendent of Dracula; c) Helen has been bitten twice and carries the vampire taint, although she is not yet one of the undead; and d) Paul and Helen fall in love and become the parents of the narrator of plot three.
Plot three: mid 1970's. Paul and Helen's eighteen year old daughter narrates. She has been raised by her father; her mother died, apparently of suicide, when she was a baby. She finds her father's dragon book in his study, and her father slowly tells her, through stories and letters, the events of plot one and two. In the midst of this, he leaves abruptly; she learns he is going to an ancient monastery in France to confront Dracula and rescue her mother, who is really alive and has been hunting the vampire all these years. She follows him to help; most of the book unfolds as she reads letters on the long train ride from England to France. She and her father confront Dracula, and are about to be destroyed when Helen arrives and shoots him through the heart with a silver bullet, reducing him to dust. The family is reunited and lives happily for many years.
Postscript: Present day: The narrator, now a respected professor of history, goes to Philadelphia to look at Bram Stoker's notes for the book, "Dracula". As she is leaving, she discovers in her briefcase a mysterious book containing only an engraved picture of a menacing dragon. (Yes, another one.) As she recoils, we end with a description of Vlad Dracul in medieval times, planning his eternal life and eventual world domination (and, presumably, extensive book collecting).