Both have points of interest, both are witty in a mildly louche way, and both are clearly (given the circles in which Cranston moved as a youth) romans a clef. Historians of the literary mainstream might find it useful to dig up the books (if they can: copies nowadays are, to put it mildly, elusive) and try to crack the code.
There are gay photographers with brutish chauffeurs, spivvish newspaper reporters, bogus mystics, venal and self-serving dons, at least one preposterous policeman - 'Sergeant Percy St Clair, a fading cherub with the movements of (a) male dancer from a ballet chorus' - and various other grotesques. There are also a good many cutting remarks made about Cambridge (Cranston studied at London University and Oxford) and some amusing juxtapositions (a clue in one book is the dust-jacket of a 'monumentally scholarly' Introduction to Spinoza being used to veil an explicitly pornographic novel).
The solution to Tomorrow We'll Be Sober rather cleverly revolves around a confusion over old London telephone exchanges (MUS for Musuem, TUD for Tudor, HAM for Hampstead, and so on) and the murderer (a weak character) is shown to have been subconsciously though innocently persuaded to do the fell deed by an obsessive psychologist; while in Philosopher's Hemlock the murderer destroys (rat- bait in the egg mayonnaise) the wrong victim. Irony abounds.
Why Cranston wrote no more genre fiction is a puzzle. He clearly enjoyed putting his friends through fictional hoops. One possible clue is his publisher. John Westhouse was a shoestring-run firm with a small and distinctly idiosyncratic list of authors, including Gerald Verner, the arch-plagiarist of the 20th century (possibly the only man since 'the abominable Curll' actually to make a living out of literary piracy), and the poet Ruthven Todd, who, when desperate for money, wrote (as 'RT Campbell') 10 books, of which to this day only six have ever been seen. Probably the experience of writing for such a ramshackle concern put Cranston off writing detective stories for life. A pity.