Meanwhile, there’s a perfectly good introduction in the GNU Make manual: https://www.gnu.org/software/make/manual/make.html#Introduct... Also available in print: https://shop.fsf.org/books-docs/gnu-make-version-381
info make
GNU tools often use man pages for a quick reference of the options, return codes, etc. Unfortunately, as info(1) isn't as well known as man(1), it's easy to miss that many GNU tools have detailed manuals.