The Timekeeper Conspiracy

This is the second book in the Time Wars series, and it's not quite as good as the first, but still pretty good: well worth reading if you liked the first.

The setting moves from 12th-century England to 17th-century France, and the Four Musketeers are involved. The plot is rather too complicated for my taste, with people of uncertain loyalty on both sides, but it makes an exciting story with some flamboyant characters.

The author correctly felt that Andre de le Croix, from the first book, was too good a character to drop, so she stays and becomes a permanent fixture. Between this second book and the third she joins the Temporal Corps, gets "implant education", and therefore becomes more like her new colleagues; which is a pity in a way but couldn't be avoided.