The later books in this series aren't as entertaining as the earlier ones. Oh, the previous one had its moments but to be honest, I think a large part of it is the whole "same plot, different antagonist" bit. Well, that and this book seemed to be rather light on the actual relationship development. Time was skipped, with the characters apart for various reasons, and what time they were together seemed to be in the middle of some sort of drama. IOW, how did they fall in love? They weren't together enough to even know what each other's full name was.
And really, I'm not sold on the whole "create mutants via experiments" theme when they seem to do just fine with that via interbreeding (the sabertoothed giant bunny from book 1 for example). In this case, they've created a mythical beastie which makes me think of the chimera series by the same author. Seems redundant.