Alec Soth - Hes so smart, and this book just blew me away the first time I saw it. The work he has done since hasn't even come close to measuring up in my opinion (http://www.alecsoth.com/Mississippi-.../frameset.html)
Joel Sternfeld - American Prospects - Inspires me every time I go out to take photographs. And all of the essays are phenomenal. The first book I found that eloquently said a lot of the things that I was struggling to say in my own work, and it came at the perfect time for me to totally embrace it. (already posted above)
Mike Smith - You're Not From Around Here - Okay so this one isn't strictly landscapes..(i suppose the other two aren't either)...and the portraits are my favorite part...but I think this book is an overlooked gem in photography. (http://www.americanplaces.org/CAPgal...mithindex.html)
Jem Southam's Landscape stories was close to making the cut, but I couldn't be TOO much like Helen...although her list was darn good.