Lewis is best known for Jack's Return Home, a very good book in itself, which was brilliantly filmed by Mike Hodges as Get Carter. Along with The Long Good Friday, and possibly Layer Cake, it's one of my favourite non-American thriller films of the "gritty" variety (I'm not sure I really like describing books as "gritty", but in a blog post, this rather tired and often misused and overused adjective is at least useful shorthand.) The novel is just being reissued by Soho Press, under the title Get Carter, and I have no hesitation in recommending it.
Lewis dies at the age of 42, after a colourful life which, like so many colourful lives, ended sadly and all too soon as a result of heavy drinking. The publicity material accompanying the Soho Press reissues includes an extract from an as yet unpublished biography of Lewis by Nick Triplow, which I found very interesting. I do hope it finds its way into print before long. Suffice to say that I've been told a bit about Lewis' life by a friend of his whom I know, and his account very much corroborates what Nick Triplow has to say.
Among Lewis' other books is Plender. I haven't read this one, but I did discuss the French film version, Le Serpent in my early days as a blogger. The other Soho Press titles coming out just now are GBH, Jack Carter's Law,and Jack Carter and the Mafia Pigeon. I gather that GBH in particular is a notable book (written towards the end of Lewis's life, when his powers as a novelist had seemed to be in decline) and I look forward to reading it.