It feels to me like Peters floundered a bit as a writer until she developed Amelia Peabody. Both Vicky Bliss and Jacqueline Kirby have whiffs of Mary-Sue-ishness that I find a bit off-putting (of course they're beautiful, slim, stacked, well dressed, and well coiffed AND clever, incisive, resourceful, AND popular with the boys), and her protagonists' sharp tongues and combative banter only reach their full potential when paired with regular sparring partners who match their irreverence and erudition. The Vicky Bliss novels only became compulsively delicious as John Smythe's (and Schmidt's) characters and relationships developed, while Amelia Peabody blossomed in part thanks to the permanent frisson provided by Emerson and augmented by her precocious son.
Without lovable and clever foils, the early Vicky and all of the Jacqueline books feel emotionally arid. They're often not merely snarky (which I love), but actually unkind, and whenever the possibility of a serious friendship or romance arises in Jacqueline's world, it's underdeveloped, shunted off the stage, or nipped in the bud. (Her oddly affectless friendship with Jean in the first book, her offstage and evidently short-lived liaisons with dishy policemen who deserved more character development in books 1 & 3, and her abortive sort-of friendship with the doomed Dubretta, to give a few examples.) And, of course, her willingness to wound, abandon, and perplex her few longer-term love interests (books 2 & 3). I suspect the latter trait is meant to parallel--with laudable feminist intent--the way male protagonists in detective/spy/thriller novels treat their female love interests, but I find it icky in either gender.
All of these less enjoyable qualities come to the fore in the 3rd Jacqueline novel, paired with a send-up of the 80s romance novel industry, which, as a subject for satire, is like shooting fish in a barrel. Yes, this is a genre outstanding for its artificiality, saccharine sentimentality, dubious aesthetics, and slender literary merit--wouldn't it be more interesting to find something else to say about it?
All of this said, I'm still planning to read the 4th & final installment in the series--just with significantly less joy and confidence that I would feel with a new Peabody novel. Because Peters is smart, her heroines are hyper-capable and proactive, and her settings are interesting, Peters is always worth reading--but she doesn't reach her potential until she starts giving her leading ladies suitable ensembles to work with.