From the first paragraph in the preface of The Art of Herge, Inventor of Tintin, 1937 to 1949. 

"The period illustrated in this second volume is fascinating on a number of counts. First of all, regarding Herge the creator and artist, it marks his maturity. The improvisation of scenes typical of his first works was over. Since The Blue Lotus his stories were thoroughly thought out and their drawing care-fully executed. The characters too became more consistent. Tintin was no longer burdened by prejudices, but thoroughly open. Some of those who had crossed his path -such as the detectives Thomson and Thompson and the villainous Rastapopoulos -had already become recurring characters seemingly indispensable to the action. Besides Tintin, Herge was the author of other successful series. Tintin had not yet achieved total pre-eminence over his other creations: the Brussels scallywags Quick and Flupke, and siblings Jo, Zette and their pet chimpanzee Jocko. Meanwhile others, who were potentially formidable or surprising, would join the young reporter: the opera-singer Bianca Castafiore, Captain Haddock, the butler Nestor, Professor Calculus. Together they represented a whole "family" of original characters who would gravitate around the central figure of Tintin to the greater enjoyment of readers".

Book is new.  Moulinsart and Last Gasp 2009. 207 pages.