In her Foreword, Harrison says, "Waylaid still reads like self-made fan fiction to me, " thereby denying book bloggers and other amateur reviewers the opportunity to use that label. Which is a shame, because that'd be a great way to sum it up. Thankfully, it saves us all from making the same joke.
In a move as classic as Uncle Jesse visiting Los Angeles to say "howdy" to Enos*, Harrison brings much beloved Rachel Morgan into the new, awesome, and in much need of publicity world of Peri Reed. Set sometime after the main events of The Witch with No Name (but not necessarily the last chapter), and before The Drafter, Waylaid will serve as a great introduction for fans of Morgan's series.
A drunken mishap, inspired by a silly Urban Fantasy TV show (that I'd totally watch), results in Jack summoning Rachel in to Peri's apartment. Jack and Peri assume she's a counter-agent who'd been waiting for them to return to attack. Rachel has no clue who they are other than nitwits who summoned her away from a date and started attacking her. It doesn't take her long to realize that her magic doesn't work, and wherever she is, it's a world she doesn't recognize -- Detroit still exists, people have technology she can only dream about, and the ley lines are deader than Arizona back home. The clock's ticking and Peri and Rachel have to team up to get Rachel back home.
It's silly, it's fun -- it's pretty faithful to both series, it hopefully helps boost sales of The Drafter and its sequel.
I don't really a lot to say without getting pretty heavy into spoilers, but I thought it was worth the pittance I spent on it, probably a little more. Fans of Harrison should give it a shot.
* I just revealed my age there, I know. I also know there are older examples, but that's the first in my memory.