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Learning Information Architecture
Don't Make Me Think!: A Common Sense Approach to Web UsabilityDon't Make Me Think!: A Common Sense Approach to Web Usability by Steve Krug
Buy new: £12.46 / Used from: £13.67
This isn't strictly about IA but if you are completely new to the field it is best to get a bit of context on usability. And this is a simple easy read.
Elements of User Experience: User-centered Design for the Web (Voices (New Riders))Elements of User Experience: User-centered Design for the Web (Voices (New Riders)) by Jesse James Garrett
Buy new: £11.75 / Used from: £14.82
Explains one perspective on where information architecture fits into the user experience field
Information Architecture for the World Wide Web: Designing Large-Scale Web SitesInformation Architecture for the World Wide Web: Designing Large-Scale Web Sites by Peter Morville
Buy new: £16.70 / Used from: £16.05
You have to read the polar bear but I wouldn't necessarily start here particularly as it is 504 pages
Communicating Design: Developing Web Site Documentation for Design and PlanningCommunicating Design: Developing Web Site Documentation for Design and Planning by Dan Brown
Buy new: £14.46 / Used from: £14.32
Rightly or wrongly, IAs are often measured on the quality of their documentation. This is a good intro to all things documentation