[eigen] recommended reading for template metaprogramming

[Mark Borgerding <mark@xxxxxxxxxxxxxx>]

I began to learn C++ 15 years ago and at some later point stopped 
ravenously devouring books and magazine articles on the subject. Since 
then, the landscape has changed considerably.

I find myself a bit confused by some (probably all) of the idioms in 
template metaprogramming.

What is a recommended book/website that explains the mechanics and 
rationale behind some of them?

-- Mark