This was a different type of sequel in the fact that the main characters from the first book, Mr. Mercedes, don't show up for quite a while.
There were some similarities between this book and Misery. We find a man obsessed with a reclusive author and his work-so obsessed, in fact, that he kills him. And then he discovers a bunch more books the author hand-wrote about his favorite character, Jimmy Gold, (Misery Chastain, if you will.) But what can he do with them now? The world knows nothing about them and he can't sell them, especially now that the guy is dead. (It might seem that some of what I've said is spoiler-y, but don't worry, it's not.)
I will say no more of the plot, other than I felt slightly disappointed. If you're any kind of mystery or crime reader at all, I would lay money down that you will correctly guess the ending of this book. (At least the ending of the main plot line, anyway.) I loathe being able to correctly guess an ending. Note that I'm careful to say the ending of the main plot line, because the real ending was creepy as hell and made me very excited to read the last book in this trilogy.
Even though I guessed the end, most of the fun in a King book is getting there, and in that regard, this story satisfied. The characters, as King's characters always are, were complex and compelling and it was nice to see Bill, Jerome and Holly again.
I listened to the audio of Finders Keepers, which was narrated by Will Patton, and he did a fine, fine job.
Recommended to fans of the King, (because after all, he is the King), but this books lacks that something which makes King books truly special.