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Affiliate Marketing Essentials
By an Amazon.com customer
Successful Affiliate Marketing for MerchantsSuccessful Affiliate Marketing for Merchants by Shawn Collins
Buy new: $20.08 / Used from: $7.99
Must-have for any affiliate manager.
The Complete Guide to Associate & Affiliate Programs on the Net: Turning Clicks Into CashThe Complete Guide to Associate & Affiliate Programs on the Net: Turning Clicks Into Cash by Daniel Gray
Buy used from: $3.54
Great overview from an affiliate perspective
Unleashing the IdeavirusUnleashing the Ideavirus by Seth Godin
Buy new: $14.00 / Used from: $3.91
The great affiliate program must have a viral aspect
AffStat Merchant ReportAffStat Merchant Report by Shawn Collins
Buy new: $149.99
Up to date benchmarks and best practices in affiliate marketing
The 22 Immutable Laws of Marketing:  Violate Them at Your Own Risk!The 22 Immutable Laws of Marketing: Violate Them at Your Own Risk! by Al Ries
Buy new: $11.51 / Used from: $1.00
Come on - you've got to always keep the basics in mind
The Tipping Point: How Little Things Can Make a Big DifferenceThe Tipping Point: How Little Things Can Make a Big Difference by Malcolm Gladwell
Buy new: $16.37 / Used from: $4.97
Thou must think out of the box
Permission Marketing : Turning Strangers Into Friends And Friends Into CustomersPermission Marketing : Turning Strangers Into Friends And Friends Into Customers by Seth Godin
Buy new: $18.00 / Used from: $3.83
Your best affiliates run opt-in lists - you'd better "get it"
The Guerrilla Marketing HandbookThe Guerrilla Marketing Handbook by Seth Godin
Buy new: $13.57 / Used from: $0.49
Some of the ideas are dated, but still a staple