Preston & Child have put out some memorable books in the past (Relic, Reliquary, IceLimit were all excellent!). However, they managed to fail miserably in their last 3 books - even though they had a very interesting character, Pendergast, to work with.
BRIMSTONE only barely managed to hold my interest: the plot was stretched-out (the price of sequelization), the villains were obvious and all style, no substance. The side stories were but page-stuffing, they added nothing to the story or the characters' development - whereas, (the partial) catharsis came in the most predictable way possible!!
This is another example of a story diluted to blandness, in order to milk the cash-cow until it bleeds...Disappointed. Again.