A separate series of books entitled "Jurassic Park Adventures" documented Eric's time on Isla Sorna (as well as other related stories) before Grant and the others arrive.
Eric Kirby is a 12-year-old dinosaur enthusiast who becomes stranded on infamous Isla Sorna after a parasailing accident. He has to survive, completely alone, on the island for eight weeks, using only his intelligence and knowledge as weapons.
Since his parents, Paul and Amanda Kirby, fail to get any help from either the US or Costa Rica government to rescue him, they resort to invite Dr. Alan Grant, thus starting all the events in the movie.
Although at first, Grant doubts that Eric is still alive, he soon discovers that the boy has managed to survive. Eric saves Grant from a pack of Velociraptors and takes him to his hiding place (an overturned supply truck). Being a dinosaur lover, Eric immediately recognizes the paleontologist and the two start forming a friendly relationship, especially after Grant learns that Eric doesn't like Ian Malcolm either.
Later, Eric is reunited with his parents and saved by Billy Brennan from a flock of murderous Pteranodons. In the end, he leaves the island with his parents; although unstated, it is hinted that Paul and Amanda reconcile and get married again. In fact, in a deleted scene from Jurassic Park III, the two of them kiss and decide to come back together for Eric, who watches them in delight.