The Trouble With Harry - Katie MacAlister
The eponymous Harry is a former spy whose wife's untimely death has left him with five incredibly willful children, so he decides the best thing to do is advertise for a new wife. After all, he's not all that fussy as long as they're sensible and clever enough not to bore him rigid.

One of the women who answers his advertisement is Plum, who's trying to escape a dodgy past where she thought she was married to a man and discovered later that the marriage wasn't the real thing, thus leaving her disgraced. Plum also has a secret of her own in that she's the author of a notorious book of sexual positions, so both her secrets are a major issue where any marriage is concerned.

The book is set in a not-quite-specified historical period that tries to be Georgian. The major problem I had with it, unlike my usual difficulty with anachronisms, was that Harry immediately falls for Plum in a major way and is delighted when he discovers she's also quite a lusty individual - this felt unlikely, given the ostensible time period, and the sex scenes somewhat overwhelm the plot (such as it is).