The UST was unbearable, I was feeling sorry for the two heroes. The first part (the ust part) is fantastic. The second part is less interesting because less believable. Unfortunately, this is the kind of book I would have given 5 stars if the end had been unhappy, or if the relationship had happened well after each of them had completed his job ( like in The Dark Horse). 
 Recommended for those who like a mega-UST.