When cooled to a temperature of 4K (-269 C), only just above the absolute zero of temperature, helium condenses to form what must surely be one of the most peculiar - and certainly one of the most intensively studied - of all liquids.
Review of "An Introduction to Liquid Helium",(2nd edition), by J. Wilks and D. S. Betts, Clarendon Press, 1987. Pp. ix+187. ISBN: 0 19 851471 9.