This novel is one of those which could come carrying a warning label: "flammatory material", or a back cover blurb including: "no liability accepted for wanton acts of a prurient nature." 
 Kushiel's Dart is fantasy without the Elves, Dwarves etc, a pseudo mediaeval and feudal Europe in which each character claims allegiance to one of the ruling gods. It also constitutes soft/hard-core pornography of various persuasions, and is laced with scenes of brutal savagery - the heroine is delightfully relieved of her skin by a tribe of hunters. 
 There's mystery and murder, minus the magic, politics between the monarchy and the ruling houses, espionage as well as traditional romance - even though the triangle angle has now been rendered old geometry, this book precedes the current fashion of threesomes and a heroine besieged with choice. In the case of Kushiel's Dart, at least the premise for such a construction is better founded than other works of fiction that don't require naming. 
 Is it tightly paced, action packed reading? I'm not sure, but I don't think so. I found it difficult to see the trees for the...ah...purple forest. I finished (by skimming chunks) of the book, and have no interest in the series. Running the gauntlet of human experiment has never really turned me on.