New listings for this turning up. It's set post-season one, so the blurb might be considered mildly spoilery in terms of the characters being more than just off on the La Sirena somewhere:
I loved what Una did with Raffi and the Romulans in The Last Best Hope (I loved everything she did in that book!), so am excited where she takes them next, and intrigued by the presumably inter-season setting.A thrilling untold adventure based on the acclaimed Star Trek: Picard TV series!
Following the explosive events seen in season one of Star Trek: Picard, Raffi Musiker finds herself torn between returning to her old life as a Starfleet Intelligence officer or something a little more tame—teaching at the Academy, perhaps. The decision is made for her though when a message from an old contact—a Romulan spy—is received, asking for immediate aid. With the help of Cristobal Rios and Dr. Agnes Jurati, and assistance from Jean-Luc Picard, Raffi decides to take on this critical mission—and quickly learns that past sins never stay buried. Finding the truth will be complicated, and deadly….