At the end of Moon Called (first book in the series), Mercy Thompson the shapeshifting mechanic, owed the local vampires a favour, and in Blood Bound they want paying back. A visiting vampire is causing problems and Stefan, (Mercy's vampire friend) wants her help whilst he tries to sort it out.
In my opinion Blood Bound is a much more tightly written story than Moon Called. We already know about the relationships, pack-conflicts and back story, so here we are able to get stuck in to the meat of the story straight away. Although I do think it's possible to read Blood Bound as a standalone, it would be much better to read Moon Called first so you've got all this rich background information in your head.
The relationships within the werewolf pack continue to evolve and I think this is far and away my favourite part of the story. Each werewolf is such an individual character and to see how they are located within the hierarchy and how they struggle or accept that, gives the story a depth it might not otherwise have had. In Blood Bound this pack structure is held in direct comparison with the more clinical vampire society, which makes for fascinating reading.
If I had a concern at all, it would be as mentioned in the other review. Mercy picks up another admirer and I think this has the potential to take away from the tension in her relationship with the two werewolves already vying for her attention.
Blood Bound is resolved very nicely, but there are enough plot threads left dangling to leave me desperately looking forward to the next book in the series - especially the new werewolf who only appears off-page here.
There will be a short story set in Mercy's world in the On the Prowl anthology released in August 2007.