I'll update this since it's still viable and wasn't necessarily answered. The #1 book you can buy is "Every Landlord's Legal Guide" from NOLO. You'll find a good description and lots of reviews on Amazon. It includes all the basics like how to advertise, screening tenants, Fair Housing law, security deposits, rent disputes, dealing with tenants, etc. It has all the state-specific laws and even tells you which state statute applies so you can research in more detail. The write is also VERY good at pointing out when you should talk to a local attorney or government to ensure you don't accidentally miss out on a local requirement.
The book comes with a CD that includes many of the forms necessary, such as a tenant application, lease agreement or month-to-month, home inspection checklist, etc. They're all in Word format and can be customized to your use. The book even includes various clauses you can add based on the situation.
I'm a PM for 120 units and am reading the latest version of this book right now and am still learning some things I didn't learn elsewhere. I can't recommend this book more!