Lycanthropes in D&D are usually depicted as savage monsters controlled by their bestial natures. They also normally have abilities beyond those of normal player characters, making them doubly un-suited to be used as PCs.
These subclasses present options for players who want to play a lycanthrope who has mastered his or her condition, and is unlocking the power inherent in the so-called "curse" over time. They are balanced against existing PHB options, with damage resistance (not immunity) coming online around level 7-9.
The werewolf is a Ranger subclass - a strong, fast warrior and hunter who can bring down any prey with tooth and claw.
The werebear is a Fighter subclass - a durable warrior who grows stronger and larger, able to claw or wrestle his way through almost anything.
The wererat is a Rogue subclass - quick, agile, and hard to kill, but not as versatile as some of the other Rogue options.
- from the publisher's blurb