'Inventor Essentials' is ok,
'Mastering Autodesk Inventor 2009' is better for content IMHO
I prefer the online tutorials, there are a lot around, here are a few:
http://mfgcommunity.autodesk.com/learning/
http://www.mcadforums.com/forums/viewforum.php?f=41&sid=a39fdccae47f8856e745004d033aafd6
http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm
There are also tutorials that ship with Inventor:
Help -> Learning Tools -> Tutorials
Help -> Learning Tools -> Skill Builders
There are many more around but that should get you started.
Regards,
Stew
Please mark as "Accept as Solution" if it answers your question or "Kudos" if you found it useful.
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Stew, AICP
Inventor Professional 2013, Autodesk Simulation Multiphysics 2013
Windows 7 x64 Core i7 32GB Ram FX2000