The Book of Dragons by Roger Lancelyn Green, illustrations by Krystyna Turska, Puffin Paperback (1973)
Roger Lancelyn Green is more famous for his collections, similar to this one, of Greek myths, stories of Ancient Egypt, Robin Hood legends, and Arthurian tales. His work was not part of my childhood, but from what I have read, many children who grew up in the 60s and 70s recall these books with fondness.
I can see why this one perhaps does not have the same level of fame. Bringing together dragon stories and trying to present them with any cohesion is a difficult task. The very act of defining what a dragon is fiendishly complicated (more so with European dragons) and further difficulties arise deciding what stories to leave out because of the plethora of myths. Where does a collector being? By geographical location? By era? By type of myth i.e. similar thematic elements?