There is an article called "recursive make considered harmful".
According to it, you should have just one Makefile.am in top level
with all the rules (all libs etc). By this, make can show its
strengths best. Often, a Makefile.am "per directory" seems to be
used, but for a new project today this should be avoided. It just
slows things down and leads to unneeded compiler calls.
I'm sorry, but where on earth did you get this terrible information?
A Makefile.am per directory is precisly what should be used, it
doesn't incure any extra compiler calls. It also makes it easy to
build seperate parts of the tree.