Authors who ultimately disappoint

I spent the weekend reading a terrific book, plenty of action, engaging and intelligent characters. I was on the edge of my seat the entire time... until I reached the last page of the book. An entire plot line was left unresolved. I knew what I expected to happen. (SPOILER ALERT) Annabelle's new friends, including the versatile former spook, Oliver Stone, would find some clever way to disarm (and probably kill) Bagger, the murderous casino owner. BUT NOOO... the book just ended with Bagger anticipating his meeting with Annabelle. Do I have to wait until the next book to see if she survives? Ah, the torture. The book, The Collectors. The author who has put me through the emotional wringer, David Baldacci.