The Ethical Slut can be thought of as a polyamory 101 book. It's
a fairly easy/quick read and contains a lot of good ideas around relationship structures, boundary setting and communication. In this book Dossie Easton and Janet Hardy have worked hard to create an interesting narrative, present anecdotal stories and leave you with workable resources.
As with any "self help" book, you likely won't agree with everything written but will probably find enough usable tools to make reading it worthwhile.
I keep a number of these on hand and loan them out to both friends and new potential lovers. "What's poly you say?", Here's a book you need to read before we go any further. :) ....no seriously, read it.
For more information on polyamory feel free to check out my poly 101 series here.