The Season Four Lost finale was the higest rated program of the week, and with good reason: the show continues to delve deeper into an intriguing mystery through a clever and original mix of flashbacks, flashforwards, and present-time scenes.
Major Lost fans might hear about the three media tie-in novels published in 2005/2006: Signs of Life by Frank Thompson, and Secret Identity and Endangered Species by Cathy Hapka. However, you should save yourselves the trouble: the books range from promising but ultimately unsatisfying (Thompson's) to just plain boring (Hapka's). Each novel centers around a new character and follow the Lost template of flashbacks mixed with present-day scenes, but nothing of consequence happens in any of the books, nor are there any insights into the island or its mysteries.
The novels could have been a wonderful addition to the Lost mythos. The show is known for throwing out far more mysteries and characters than it's likely to be able to deal with in the episodes that are left, so letting each novel reveal the truth behind one of the smaller mysteries (the four-toed statue, the hatch blast-door map, the parachute food drop, etc.) or shine a spotlight on one of the ancillary characters (Arzt, the Other's Sheriff, Rousseau, etc.) would have been a great way to draw in committed fans without alienating the t.v. show viewers who only care about whether Kate's going to end up with Jack or Sawyer.
A well-coordinated media tie-in novel could add to the show's depth and would ultimately sell more copies than the quick, unsuccessful cash-ins that these novels were.