Note that there are different publication cultures among the different scientific disciplines. In some disciplines, journals are the primary publication venue where conference papers have only little if any value. In Artificial Intelligence, this is not (at all) the case. Here, conference publications are the primary means to distribute knowledge. Still, journal articles (at top-tier venues) are regarded highly prestigious, but they are not the primary means to publish cutting-edge research, but often re-elaborate established research and provide some further results.
Book chapters on the other hand are usually not (at all) hard to get accepted. Rather than presenting cutting-edge research they elaborate in more detail on some work that is already published, fitting to the theme of the respective book.