Do not read the manual! Real men do not read manuals 
Although, coming from a 40D, you should be at home with most settings within an hour or two.
The youtube channel I posted earlier is VERY good and you should sub to it as the guy goes through, in detail, all the good bits of the 5D III.
Edit*
I absolutely love this camera for landscapes, SO sharp and SO much resolving power!
http://robbiekhan.co.uk/root/temp/5D3_0197.jpg

Although, coming from a 40D, you should be at home with most settings within an hour or two.
The youtube channel I posted earlier is VERY good and you should sub to it as the guy goes through, in detail, all the good bits of the 5D III.
Edit*
I absolutely love this camera for landscapes, SO sharp and SO much resolving power!
http://robbiekhan.co.uk/root/temp/5D3_0197.jpg
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