I'm trying to compile glibc in chapter 6, and have carried out the configure and make OK, but when I do 'make install' it falls over when trying to copy libc.a over to /usr/lib - reporting it is not a directory.
I looked at /usr/lib and sure enough it isn't a directory, but a link to another file elsewhere (can't remember which off the top of my head). So it seems like a symbolic link has been wrongly setup for /usr/lib sometime previously?
Can anyone think of why this has happened?

There shouldn't be any symlinks for /usr/lib. Most likely what happened to get it like that is you entered the a link for a library backwards.. .. create a link from /usr/lib to the library stead of the other way round.

There are ways of removing links.. however I would NOT be the one to tell you how, as the last link I tried to remove I ended up removing a critical system file stead of the link.

Look to see what file it is linked to and back step to that point. You might be able to get away with just backsteping to that point and installing from then on (after the link is removed) or you might end up having to start all over... ..

On page 107 of the book there is the line:
ln -s /tools/lib/libgcc_s.so.1 /usr/lib
which I would have used, and that appears to make a symbolic link /usr/lib pointing to /tools/lib/libgcc_s.so.1.

So is the book in error here?

Works for me. That command installs a symbolic link in /usr/lib pointing at the libgcc_s.so.1 in /tools/lib