Meet the Tiger
(later retitled "The Saint meets the Tiger") published in 1928, was Leslie Charteris's first book in the Saint Saga (even though Hodder & Stoughton later pretended that "Enter the Saint" was, presumably because they weren't the publishers of the former).
Nevertheless, "Enter the Saint" is the book that introduces Simon Templar as he is in most of the books that follow, and as neither the cinema nor television has yet had the nerve to portray him: he beats people up, robs them, blackmails them, even murders them, and gets away with it. And the fact that his victims are particularly vicious thugs (Snake Ganning), dope dealers (Edgar Hayn), white slavers, war profiteers and so forth — and that he gives a large chunk of his profits to charity — would not excuse him to a strict moralist. The success of the Saint books for seventy years must mean that strict moralists are perhaps not as common as one ought to hope.
There are three longish stories; a reference that may be presumed to be to Sir John Bittle (from "Meet The Tiger") dates the first at nine months after the end of that opus.
To enumerate plot details would probably be superfluous. Suffice it to say that Charteris was just starting to hit his stride, and that "Enter" introduces two of his best characters: the Saint's friend Roger Conway, and his perpetual adversary, Inspector Claud Eustace Teal. Patricia Holm now lives with the Saint although (daringly for 1930) they aren't married, and Orace is still the stalwart retainer.
A fine warm up to its sequel, what is possibly the best of all the Saint stories: The Last Hero
(aka "The Saint Closes the Case").
P.S. For a list of all Charteris's Saint books (in two sections, because of length limitations) see my Listmanias.