The books are very much all about the sexual tension between Robin and Cormoran; the plots are almost an afterthought! I struggled with The Inkblack Heart because of the text format (multiple chat room conversations happening at the same time) and I never really engaged with the plot. All the others have been enjoyable if overly long and they can take a while to get going (which is just JKR's style). As a Blue Öyster Cult fan, I really liked Career of Evil! Obvs you have to read them in order to understand the wider character and story arcs.