In brain size Neanderthals were comparable to modern humans or even slightly larger--the Neanderthals ranged from 1300 to 1700 milliliters whereas modern humans range from 1200 to 1400.
There is a recent scholarly (but very readable) book on the Neanderthals, originally published in German in 2005, English translation 2009: The Neanderthals, by Friedemann Schrenk and Stephanie Mu+ller, translated by Phyllis G. Jestice, published by Routledge (paperback ISBN 978-0-415-42420-9). No National Geographic-style color photos but lots of interesting black-and-white drawings and maps--a very interesting book with up-to-date information.
The Neander Valley, by the way, is named for Joachim Neumann, a Bremen theologian and hymn-writer of the 17th century (composer of "Praise to the Lord, the Almighty, the King of Creation"). Neumann means "new man" and "Neander" was coined from the Greek roots neo- and andr- meaning "new man."
“Neanderthal” means Neander Valley auf Deutsch... Basically just a place name.