The Black Island was published as a black & white book in 1938, then in 1943, the very same B/W drawings were coloured with only one frame added. Then, in 1965, on his British publishers' request, Herge had to re-draw the whole book modernizing and changing every frame, creating the common book we grew up with. In this 1943 original, you get to see the all-Herge vision of Tintin's deeds in Britain, unlike the 1965 version which was largely drawn by his associates in "Studio Herge".
This adventure was created while the clouds of war were gathering over Europe, and Herge did not miss that. Tintin goes to Britian after a money counterfeiting gang headed by a man called Müller, and although Müller's nationality was never mentioned candidly in the book, you do not need much guess work to figure it out. History tells us that after the end of WW2, documentation of a massive operation to forge British money by the Nazis was discovered. Their aim was to destroy the British wartime economy, an aim they never achieved. For Herge to draw this book before WW2 even began, just shows the kind of visionary he was.
Released with this book are 5 other exact copies of first colour editions: "Cigars of The Pharaoh", "Broken Ear", "King Ottokar's Sceptre", "Tintin in America", and "Blue Lotus". Those five are slighty to significantly different than the common ones you already have. Real hardcore Tintin fans should get the whole set of 6, but if you were going the get just one, it definitely should be The Black Island. 100% different, historically important, charming, and simply beautiful.