Before the girls and the pop hits came along,Fleetwood Mac was a great blues band founded by Peter Green.From 1967 to 1969 they were the top blues band in England.Absolutely right.
They actually have two albums that are titled only "Fleetwood Mac" - one from 1968 and one from 1975. They bear virtually no resemblance to each other. The first is great blues stuff in the vein of John Mayall's Bluesbreakers and the other much more pop oriented.
You'll miss some good stuff if you ignore the earlier period.