Twitter guides are no longer the new black, but a classic trend in the business.
About all PR and marketing companies offer a Twitter for Business, or Twitter for Beginners guide, in an effort to appear as authorities in the field. 
As many other similar products, “How to Use Twitter for Business – An Introductory Guide” for 2011 attempts to teach you how to use Twitter to:
- Develop and promote your brand
- Interact and support your customer base
- Monitor what people are saying about your company and brand
- Create buzz around upcoming promotions and events
- Promote thought leadership content you’ve created
- Develop direct relationships with bloggers and journalists for public relations success
- Generate leads!
If you’d like to try other eBooks, I personally recommend The Social Media Newbie’s Guide to Twitter for Businesses by Alina Popescu, also a free eBook, seasoned with a great tips, and advice on how not to use Twitter for business as well.