Long story short: This product is great and you should probably buy it.
Long story long: The matter of non-evil undead and necromancy has been a source for plenty of debate, but no matter which side of that argument one may fall on it's undeniable that supporting material for such themes has been sorely lacking since Third Edition began.
The White Necromancer remedied that problem in a big way when it debuted in Kobold Quarterly, and this expansion of the class essentially seals its status as the place to go for unambiguously heroic necromancers. There's no automatic assumption of evil in undead or necromancy here; the matter of "how" and "why" are put forth as the deciding factor.
These necromancers aren't your stereotypical villains nor are they forced to be questionable anti-heroes, though there is room for the latter. Rather than focusing on enslaving and defiling the dead, the white necromancer is focused on working with or even for the dead. The class is more about those who help lost souls find peace or treat with the dead for aid than seeking power over them and the living.
This alternate approach is built right into their mechanics, where raising undead aid is as much a matter of diplomacy as magic. And this doesn't grant a white necromancer complete control over such undead, as they are fully free-willed beings that must be treated with respect. Coupled with their ability to make non-evil undead through this manner, the white necromancer's approach can add a lot to a setting and a campaign as demonstrated in the short introduction featuring a necromancer seeking the aid a long dead hero against his evil living descendant.
Not only does this readily enable all sorts of non-evil undead NPCs to fulfill different roles throughout a setting, from truly noble necropolis guardians to spectral family guardians, but it also gives GMs a cool way to communicate the history and lore of their setting.
And for those that may be worried that this makes white necromancers out to be all rainbows and sunshine, don't worry. While you certainly could play one that way, there's plenty of dark and macabre flavor built into the class abilities and spell list, from the various new bone-centric spells to the Grasp of the Dead ability. This product certainly delivers on the Dark Is Not Evil trope.
The two new archetypes really expand the character possibilities for the class as well. The Necrotic Healer offers perhaps one of the most heroic and self-sacrificing examples of the "healer" role ever, taking the standard White Necromancer's self-sacrificing healing abilities and running full tilt with them to make characters that take on the wounds and ailments of others. It's a potent and potentially high-risk approach to healing.
The Grave-Bound archetype gains an undead companion at 5th level, choosing between six general types(ghost, mummy, shadow, skeleton, vampire, or zombie). Each type is rebalanced according to the white necromancer's level with their own distinct progressions as they advance. The exact nature of the necromancer and companion's relationship is left undefined, lending itself to a wide variety of possibilities, from the wayward scholar trying to solve her spouse's murder alongside that spouse to the noble who inherited his ancestor's mummy bodyguard to the ghost whisperer who accumulates the regrets of the restless dead into a shadowy mass that she's working to put to rest or even just someone who's childhood pet's loyalty keeps him at his master's side beyond death.
There is a lot to play with here. And fans of Jakandor or Eberron's Undying Court that have been left hungering for that sort of macabre and alien flavor without having to wrestle with current default assumptions will likely feel right at home with this product's approach to necromancy.
The Expanded White Necromancer tackles some themes that many have been longing for for quite some time and that have gone untouched for far too long. And it pulls it off perfectly.