From the back cover:
In this follow-up to Morgenstern's Spellbook, we present over 70 new spells spanning 12 classes. Collected by the bard Resnet Morgenstern, sister to the great Rasmus Morgenstern, these spells represent her life's work as a collector of rare knowledge.
This book makes an excellent companion to Morgenstern's Spellbook, but stands equally well on its own.
Resnet's Spellbook works well as a "random" treasure item, the showpiece of an NPC's private library, or (broken into volumes) as the hook for an item-collection plot, especially when used in conjunction with Morgenstern's Spellbook. It is also an excellent source of a la carte spells to revitalize you campaign.