Plenty of Warhammer 40,000 novels have been written from the perspective of humans and space marines, but it took a while before Games Workshop really got into publishing books from the perspective of 40K's many alien species. If you're into orks I recommend Ghazghkull Thraka: Prophet of the Waaagh, and for swashbuckling aeldari pirates there's Voidscarred, but the peak remains The Infinite and the Divine by Robert Rath.
It's the story of a long-term feud between two necrons, Orikan the Diviner and Trazyn the Infinite, immortal robots who were once flesh-and-blood and went a bit loopy in the uploading process. An argument over who owns a particular artifact becomes a heated rivalry (not in the sexy way, though now that you mention it…) that encompasses, as Games Workshop's own summary puts it, "clashing with Exodite armies, xenos uprisings, and a spell in Necron small claims court."
