Books don't translate well, since much of the action is pre-scripted in cool ways that can't be replicated in gaming, the story is made to be PASSIVE, not interactive, and finally, much of the insight and story comes from the thoughts of the characters, which are either omitted altogether (making for a confusingly garbled story), or are included which creates way too much dialogue and cutscenes. Basically, only in circumstances where you can deviate from the written account, such as the Watchmen's The End Is Nigh, which takes place before the book. Another good example is Lord of The Rings Conquest, where the story does not focus on the main characters, allowing the developer to create a more interactive storyline and can create abilities tailored to good gameplay, not ones that "need" to be shoe-horned in to give the game the same feel as the book (most of these are impossible to include in gameplay without dumbing them down, which pisses off the fans).
Star Wars: Knights of the Old Republic and Co. are good ideas, because they don't interrupt the popular continuity, even though they dumbed down signature moves, it felt like Star Wars because Bioware kept to the Star Wars ideals while creating a unique story that didn't ruin continuity, which is VERY difficult.
Basically, unless you are a visionary or a genius, just stay away.
Star Wars: Knights of the Old Republic and Co. are good ideas, because they don't interrupt the popular continuity, even though they dumbed down signature moves, it felt like Star Wars because Bioware kept to the Star Wars ideals while creating a unique story that didn't ruin continuity, which is VERY difficult.
Basically, unless you are a visionary or a genius, just stay away.