Storm Warning is one of Richard Castle's very successful Derrick Storm novel, written by Richard Castle in the years before he met Beckett. Although referenced in the show, unlike some other Storm books, it has never been made available in the real world.
(from richardcastle.net) When Derrick Storm’s close friend, Attorney Sam Strummel, is murdered in cold blood in a cemetery outside of NYC, Storm launches his own investigation to bring the murderer to justice. While investigating Strummel’s business dealings, Storm exposes a murder-for-hire syndicate that has just made him their next target.
References in Episodes
In Fool Me Once (episode 2.4) , Castle and Beckett meet a CIA agent, Agent Gray, whom Castle interviewed for research on secret agents for the book. As the three talk, Gray uses the expression "Transparency gets you killed," a quote which Beckett recognizes as having been used in the book.